Nvidia seems unlikely for MP as the next-gen systems coming out now are discrete AMD. Even the integrated stuff has moved from Nvidia to Intel.
For better or for worse, I don't think Nvidia is in the cards for this next go-round. Maybe next time, maybe not.
Whatever your personal thoughts are about CUDA, don't forget that Apple had to do a hell of a lot of recalls due to Nvidia, and Nvidia outright lied about what was affected. Maybe Apple got burned and decided to kick Nvidia to the curb for a while.
So my personal prediction is 6970 and 6870. (Even PC 6870s can be made to work right now, so that one's a no-brainer.)