So far, we know virtually nothing about book 2 of The Legend of Korra, and I know some of us would kill to get a decent trailer from the creators. But for the time being, I will compile what we know about the series so far, what the creators have given us about book 2, and info from anonymous sources and try to provide decent speculation about Book 2.
I want to start out by saying that in book one, they really screwed people who thought that Aang was Amon. I didn't think so, and I thought that that was a very dumb assumption, but most of us thought it was going to be someone who we knew was going to be in the series or someone who we already knew. (I feel like they just kind of dropped Noahtuk down on the table out of nowhere.) But this shows how unpredictable the creators can be with this series, or how much they can cram into one season... but whatever.
So already, we have the comic con interview, a sketchy trailer, some hints from the cast, and the nickelodeon upfront (not really important). The biggest chunk of information we have was from comic con. So far we know that it is going to take place around 6 months after the defeat of Amon, it starts out in a party at the southern water tribe, korra has a fight with a spirit, sometime during the course of book 2 they talk about the first avatars and they go to the southern air temple and book 2 is more spiritual yada yada yada... that is only the most important stuff. What we all really know is that we are all dieing to see book 2.
So I don't want to bore anyone to death so I'll just make my speculation breif:
If we put all of this together we get similar information. We have all of these spiritual events and we know that the second season is formed around spiritual sides of the avatar. So my speeculation is that they are at the water tribe party but there are spiritual problems about. Korra tries to find a spirit spotted around the area and is attacked. They fight and Korra somehow fights it off only barely. Some things happen and she needs a spiritual tutor so that she can travel to the spirit world so that she can stop the conflict. She goes to the northern water tribe to be tutored by her uncle. During the remainder of the season, she has lessons and she might come in contact with a problem in the spirit world associated with the fall of the airbenders or aang so she travels to the southern air temple and she might go in the hall of statues. Then she resolves the conflict with the spiris and the season ends.... My speculation happy face :P