Toy Story 3 will be presented in a theatrical aspect ratio of 1.85:1; so says director Lee Unkrich who answered my question about this around an hour ago on Twitter, @leeunkrich!
IMDb has been saying 1.85:1 for a while but the site can be unreliable on technical specs during production. Makes sense considering the first two films in the series were in the same aspect ratio.
Of Pixar's first ten masterpieces five (Toy Story, Toy Story 2, Monsters, Inc., Finding Nemo, and Up) were 'shot' in 1.85:1 while the rest (A Bug's Life, The Incredibles, Cars, Ratatouille, and WALL-E) were framed in the wider 2.35:1.
As I tweeted: "Only a true nerd would want to know this". Yeah.