It occurred to me that the success of Korra could motivate Nick to try their hand (and presumably M. Night's) at a second installment in the film trilogy.
Originally, Nick had planned to make Avatar their "Harry Potter" and, according to Wikipedia, timed the release of the first movie with a marketing push. That makes sense, since Korra was announced in 2010. This was an obvious move/business strategy, since Avatar was making so much money and popularlity hadn't seemed to wane. The latter was confirmed by the legion of disappointed fans after the movie (read: atrocity) came out.
Now with Korra, Nick has seen that Avatar-enthusiasm is still going very, very strong. Some viewers are just about too young to remember the previous series or film well--aka, a "new generation" of sorts. This is a cool thing because the magic of Avatar can be carried forward, but Nick could rightly interpret it as a chance to reintroduce the movie franchise. And frankly, I have no faith that M. Night, if he stays on, will make anything good come of this second chance.
The Avatar universe has great potential for expansion in the next few years: Korra's books 2 through 4 can easily push marketing and the creation of new media (like comics). But I hope that any attempted movies will be animated (adventures of the older Gaang?) or at least be helmed by a different director who can reboot the film franchise. A director who, presumably, has watched the entire series.