During Celebration II on Saturday I (Chris) caught up with Peter Mayhew at his autograph booth. We talked for a small bit and during the conversation I asked about the reports that he filmed a "celebration scene" as Chewbacca for Episode II.

Mayhew said he filmed nothing for Episode II. That he had said something else and that "some people on the Internet blew it out of proportion." When asked if Chewbacca would return, he said that he doesn't know if Chewie will be back in Episode III, at all. "No one has told me," he said.

However...

Mayhew did say that he found that of all the classic trilogy characters, Chewbacca is the only one that Hasbro is making plans to make additional figures of: that they're studying new sculpts of him. Add that to Mayhew's reiterating Lucas's promise that if Chewie returns to the saga, Mayhew would be the first to know and would definitely ask Mayhew to reprise the role. Mayhew was apparently very pleased when he mentioned these things.