|Bob Peterson (R) with Up producer Jonas Rivera in 2010|
This remains unconfirmed, but Peterson was indeed a no-show at the D23 Expo earlier this month, where other members of the production team previewed the film for attendees. Pixar has not yet commented.
While changes at the helm are always worrying, this is nothing new at Pixar, of course, having happened on Toy Story 2, Ratatouille, Cars 2, and most recently, Brave. At least this puts away the theory that Brenda Chapman was replaced as director of Brave for being a woman.
Update (Aug. 30): Pixar president Ed Catmull confirms to the Los Angeles Times' Movies Now blog that Peterson is no longer directing, however a replacement has not yet been named.
"Sometimes directors ... are so deeply embedded in their ideas it actually takes someone else to finish it up. I would go so far as to argue that a lot of live-action films would be better off with that same process," Catmull told the Times.
According to general manager Jim Morris, Peterson is still at Pixar, directing another in-development project. "Bob is still working at the studio, and we hope he will stay here for the rest of his natural life."