I've been thinking about this lately. At first, I thought that Tangled was going to be good enough to take The Illusionist out of the potential candidates list, and while it is a really good movie, I'm not sure if that's going to happen.
TS3 is a definite, and while Tangled and How to Train Your Dragon are also great animated movies with a likely hood to earn a spot, it's worth noting that both movies aren't something you haven't seen before. Tangled is a traditional Disney fairy tale while HTTYD is a boy spiritually bounds with non-human creature story that you haven't seen in a movie in a while.
Both films are probably one of the better examples of both story types, but HTTYD probably has the edge because it's not something you've seen from Dreamworks, at least not in a good while. There are plenty of Disney fairy tales(heck, we got Princess and the Frog last year), but it's not every day that we get a Dreamworks movie with little childish or "adult" humor and almost all heart and story.
Although I wouldn't count out a repeat of 2008, where we got three movies from the mainstream studios. Granted, that mostly happened since Waltz With Bashir got a Best Foreign Picture nominee, so that probably isn't going to be the case.
