My understanding is that they are just moving and the current characters would be reorganized. I wouldn't be surprised if Woody and Jessie got moved into Donald's spot and Pinocchio got Daisy's spot. I haven't heard that, just pure speculation.
There are some rumored "tomorrowlandish" characters moving to MK which would likely replace Chip and Dale, but that means we would probably lose 2 characters elsewhere to make it an even swap. Maybe Stitch will get the boot when his attraction goes into rehab (rumored to be removed completely). The only other easy character I can think to cut is White Rabbit?
I'm the most interested in this. Peter was always a main staple in Adventureland (as was Hook and Smee), but once The Pirates League moved in, those characters were kicked out due to inconsistent storytelling. Jack Sparrow couldn't be there, since his show is so close, and that creates some Character Integrity issues.
On the other hand... the Jake option is rumored to be at the League within the month, so maybe Jake will get added... then again, Jake is in the same storyline as Peter... so many quandaries!!! The M&G is beautiful where it is, so I hope they find something!!
The one thing that's safe to say is that with all the expansion going on... I've heard nothing to indicate the character budget is expanding. So Entertainment has to be very resourceful with the characters they currently have and try to spread the wealth throughout the entire park.