An oft-quoted problem which is claimed to be endgame material for "Tokka's" chances in the "Tokka" vs. "Sukka" love triangle is the problem of the three year age difference between Toph and Sokka. The following is a re-analysis of this supposed problem, which I hope in the processes will identify whether this really ever ought to have been a problem in the series and, if so, whether this still must be the case for the main portion of "The Promise" graphic novel series (which takes place a year after the series finale's end point). The age problem, as I see it, is three-fold: 1) the problem of age as it reflects the internal psychological development of the characters, 2) the problem of age as it reflects the external attractiveness of Toph's appearances (appearances not even being possible as a major theme in the opposite direction because of Toph's blindness), and 3) the problem of age as it reflects the social development of the characters.
The psychological problem of age is that Toph had not yet reached a certain turning point in her interior mental development during the series, which Sokka had already passed and which no relative deepness of mind for her age on her part could really remedy; because of this, any possible relationship between the two of them could not be one of empathetic equals, but would require the one who had crossed the line (aka Sokka) to pre-dominate over the other (aka Toph) mentally, causing a severe repression of development of an inner sense of self which is rightly called pedophilia (as the line in question is that of puberty). As Toph has clearly passed this point by the time of "The Promise", the mental coercive factor indicated as having to exist in any romantic relationship possible between the two during the series may be seen as no longer a major issue for the two of them.
Addressing the second point is a particularly difficult process for me, as I generally hold myself to attempting to ignore outward appearances, especially where my favorite character is involved - concentrating on her appearance would inhibit my long-term goal of understanding her given psychology, her characteristic vices, and her characteristic virtues. Nevertheless, I would be being very honest with myself or the public if I discounted the place of appearances in romantic relationships altogether.
There is a sort of physical attraction to another person which is totally displaced from one's sense of self; this is the notion which the “Zutara” of passion is built upon, and is basically how “Sukka” works in-canon for both of its members. There is another sort of physical attraction, however, which is built upon the other person's continual seeking of one's good on the basis of their romantically-based empathy for one's self regardless of the circumstances or one's disposition towards them, which magnifies their immediately apparent attractiveness out of a wonder in what they could possibly consider beautiful in oneself that could possibly justify to them such a continual aiming of good one's way. This mental beautification of the other which resides in the high romantic esteem in which they hold oneself may overcome any boundary provided by plainness in the part of the other, being restricted only by that which causes one to immediately turn one's attention away in disgust at the thought (should the thought ever even come into one's consciousness in the first place). This would also tend to be more long-lasting than the more strictly outward-pointing form of physical attraction, as the latter can easily be displaced from its object by the appearance of a more attractive-seeming person and requires a great deal of work to even be desired as holding to one object, while the former rests more solidly upon one's own inward self-concern and makes the matter come more smoothly along with one's own desire to build oneself up when it is to one's own good. This is the basis on which “Kataang” eventually worked within the series itself, overcoming the immediate lack of attraction that an older girl might have towards a boy younger than herself; the possible psychological barrier initially existed in "Tokka" between the two of them never having been a real issue for them, Aang having been well past the dividing line of puberty by the time Katara began to seriously consider him as a romantic option. As Toph is not physically unattractive, and is no longer of the age in which the thought of romantic attraction to her would be repulsive to any well-constituted mind beyond the dividing line of puberty, in "The Promise" this as well need not be a significant factor any longer - stronger would be the type of personal support Sokka chooses to turn his gaze towards in the end.
The third problem of the age difference is tied to the first two, yet is more than the sum of their parts. Obviously, the social development of both characters would have been inhibited had they entered into a mentally coercive relationship in which Sokka was not truly attracted to Toph (though Toph would be inhibited more so than Sokka), but this does not mean that her development past the puberty line in "The Promise" removes the social issue of their age difference. So, the question is, would Sokka's going out with a pretty young teenage girl (Toph) as a matter of choice over a more obviously beautiful older woman (Suki) ultimately work to slow his social development, and would it do the same to Toph's?
Under preferable conditions, where the characters in question have responded to their circumstances with a mature (or at the very least, a mediocre) frame of mind, the answer to the last question would be yes; the social problem of the age difference in a potential "Tokka" relationship would remain despite a year having passed, as Sokka would have long since developed his place in society and joined other people within his age set, and Toph would have joined that age set considered appropriate for a young teenage girl. As Waterkai pointed out, anyone one who has successfully tacked themselves on to the proper age set will have a different sphere of interest and will therefore hold different social interests than a member of another age set (whether above them or below them in age). However, the characters both responded to their adverse circumstances immaturely, and have shown an empathetic concern for one another's person in such circumstances, and thus this rule does not apply in full force. The simple matter of saying this may be taken as a sign of disrespect towards the characters in the views of some ("is it not disrespectful to say they don't socialize as society expects of them?" being the general train of thought), but in reality many people are "dorks" and don't fit with society's expectations of them for one reason or another, and it is more respectful to treat a character truthfully in regards to this subject without being biased against them because of it than it is to falsely skew their social development in a direction which it actually does not align with (which shows an overpowering disrespect for the differences they may have from the norm). It ought to be admitted as a sign of respect for the characters, then, that (if only as friends) Toph needs Sokka around to provide a more mature sense of duty to other people which she herself does not have, and Sokka needs Toph around to provide a more youthful sense of mental remold-ability (which partially comes of the fact that Toph is a deeper thinker for her age than Sokka is for his) to prevent him from becoming stuck in his immature ways as a matter of life-long habit. One may object that the more mature Suki may be able to get Sokka to mature more effectively than Sokka ever could; however, because Suki lacks a visible empathetic understanding of Sokka's situation, such a push to mature him would come as if imposed from above himself and not as reflected upon down next to his own situation as a guide upward, and would not truly motivate him to mature socially on a consistent basis but instead only when Suki demands it of him. As each already needs the other to help them develop socially, to prevent them from remaining at an abnormal level of immaturity throughout their lives, this should override the social age problem from practical consideration, anything else being a mere surface-level, subjective critique that is not ultimately grounded in the reality of the character development, and which thus ultimately does not hold water.
Finally, these fortuitous developments for "Tokka" concerning its placement in the "Tokka" vs. "Sukka" love triangle do not necessarily mean that the relationship would have to come to a romantic conclusion in "The Promise" itself; the possibility exists that "Sukka" could simply break down of its own accord in said comic, with it being heavily implied by the plot developments (so far as these things go) that Toph and Sokka's relationship is heading toward a romantic conclusion, but with said implied conclusion only being confirmed outside of the comic itself. For those who say that Sokka must be in a relationship in order to be respected as a character and who use this as their explanation why "Sukka" had to be the original series’ concluding ship of the two, one might point them to a more likely seeming conclusion: the "Sukka" relationship had to exist at the end of the series so that Sokka would have some sense of his ideals having been preserved (represented as they were to him in the form of Suki) and be respected as a character on that account. If the theory of increasing "Sukka" polarization over time is correct, however, this will probably not continue to be the case at the end of "The Promise", and thus the necessity of "Sukka's" existence is lost.
To pre-assume that a character must be in a romantic relationship in order to be respectable, is actually a sign of disrespect of the character on the part of the fan; to assume such is to assume that the character's psychology must be held within the confines of the process of finding a mater, reducing the individual under study to the level of an animal. If their development as a character requires them to be ripped out of a romantic context in order for the details of their given psychology to be respected, so be it; many teenage romantic relationships tend to be unstable (as the writer of "The Promise" Gene Yang also says), and it is better to abstain from that which tends to make one unstable then to remain within it, regardless of what the de-stabilizer actually is. If this turns out to be true in Sokka's case, it would be more respectful of his character to remove him from romantic relationships than to keep him within one, while still implying the general turn-out. As the status of Sokka's relationships is hardly the point of the plot, the difficulty of leaving such a thing implied if need be would be moderated, as the more important developments in the story could be called upon to intervene within the story whenever an obvious conclusion would otherwise necessarily be written (this is the major problem of all shipping-based fanons).
Agree or disagree, please state your thoughts on the above analysis of the age problem for "Tokka" in the comments section below.