Actually, isn't this something Fox was working on for a while? I seem to recall that Joss Whedon was working on the screenplay, and really psyched about it because he wanted to do a musical.
Like Disney did, claiming Toy Story 2 didn't count? :) Not that we should be looking at this as "Disney bad, Pixar good" or vice versa. What Pixar wants is a deal like George Lucas has with Fox for the Star Wars prequels, and they've got a chance of getting one for the same reason - their...