I doubt that it would be MF. Canon will release a high MP Camera only in direct competition to the d800.
I sure hope that they price the big MP camera is priced in line with the D800. At $8-10K, it may be worth my while to switch.
High MP camera: Nikon $6K lower price
200-400 F4: Nikon $3K lower price though Canon may be a tad lighter and have a built-in 1.4
500/600 F4: Nikon $3K lower price though Canon is a lighter and perhaps a bit sharper
Save $10-12K on upgrades/new equipment. That is significant.
The advantage (availability) of APS-H sensor appears to be gone.