While I generally do not like to deal in speculation, there's enough stuff flying around to make this worthy of note here. Much of this information has been compiled on Henry Pott's Yes (Where are They Now) page, located HERE.
Yes to re-group with a world tour
Yes have new management and are in negotiations around a North American tour this summer, coinciding with their 40th anniversary.
Who will be in the band?
The band will include Anderson, Squire, Howe and White, but it appears that they will be without Rick Wakeman. Reports suggest that Oliver Wakeman, Rick's eldest son, will plays keys instead. The key point of contention seems to have been the length of the tour. Chatting with fans after a solo show in early Nov, Wakeman confirmed he had been in discussions with the others about touring in 2008 and that he wants to do a tour, but that they could not agree on what form the tour should take. He explained that he is limiting himself to 25 shows a year, but that the others want to do a tour of over 100 dates. He was quoted as saying, "They're mad—Jon's voice would never stand up to it." Wakeman has semi-retired from touring.
New music is also planned: in a late 2007 interview, Squire said:
"The thing about Yes is we've always challenged ourselves to do different things, bring different things out, approach music differently, and stretch the boundaries of our capabilities under the banner of it being Yes. Next time when we're in the studio, which might be in a years' time or something like that, I'm sure we'll look at certain ways of doing things in a different fashion. Some things will work, some won't - but we'll give it a go."
In a Nov 2007 Notes from the Edge interview, asked what he saw as the major goal for Yes in 2008, Squire said, "Well, it would just be nice to playing to people again and that stuff. Hope everyone has a good time, enjoys it. As far as an actual set list, we haven't really discussed that yet."
There's loads more information on the site linked above which goes into some greater depth on the whole evolving situation.