According to Mouseplanet.com:
We hear that the following are appearing at Star Wars Weekends, though the only dates confirmed are Daniel Logan for the first weekend: Jerome Blake (Rune Haako, Mas Amedda and others), Warwick Davis (Wicket the Ewok, Wald), Daniel Logan (Young Boba Fett), Peter Mayhew (Chewbacca), Don Bies (Master Puppeter and Creative Maker) and Rob Coleman (Master Digital Creature Crafter, Leader of ILM animation for Episode III).
I checked all their personal websites and Peter Mayhew is saying he will be there on May 27 - 29. Noone else has any dates actually posted yet.
I'm thinking next Monday for an actual list, after Celebration III is over?