In that case, I'd expect over a quarter of the character info to change. Here is what Disney has announced:
This fall
Periwinkle joins Tinker Bell's Nook
New Belle M&G at MK
New Ariel M&G at MK
Pete's Silly Sideshow with Minnie, Daisy, Donald, and Goofy at MK
Ralph at DHS
Unknown
Beastly Bazaar opens at DAK
Next fall (2013)
New Princess Hall for Cindy, Rapunzel, Aurora, etc at MK
Here are rumored changes that Disney hasn't commented on:
This fall
Beast leaving Epcot, going to Be Our Guest Restaurant at MK
Marie leaving Epcot, going to Main Street MK
Mrs Incredible leaving DHS
Gaston joining MK lineup
Unknown
Chip & Dale relocating from Tomorrowland to Frontierland
Camp M/M closing and characters relocating at DAK
Winnie the Pooh and friends leaving DAK
Character Spot being remodeled at EC
There are more rumors out there but these have the most credit. There are also more changes that haven't hit the on-line rumor ville yet - stay tuned...