Epcot certainly has the most credible rumors right now (and there are a lot of them)
I haven't, nor has anyone else here that i've seen, mentioned anything about MK rumors all that much outside of this thread. It's not like we should be expecting a bunch of new builds, but Tomorrowland is up for a possible complete overhaul for the 50th and there's still faint talk of the Frontierland ride, although I believe that has died off a bit with Tomorrowland now being the main focus.
Pretty much everything in Tomorrowland (sans Peoplemover and CoP) for an overhaul and there is a potential for a new build, but it's all in the air right now. For example, the Wreck-it Ralph stuff people thought was definite back late last year is actually almost unlikely now.