Buried in a news story about The Avengers going 3-D was a totally separate, incredibly fascinating piece of news: Disney announced that its previously untitled Pixar movie, coming in November 2013, is called Frozen. And it's about an Earth where an asteroid didn't hit and wipe out the dinosaurs, and thus the dinosaurs kept evolving. And yes, that sounds fantastic.
Update: According to Slashfilm, Frozen is actually an adaptation of Hans Christian Andersen's The Snow Queen, which makes sense with the title. And Pixar's untitled dinosaur movie is still untitled, and won't be coming in November 2013 after all.