I hope they make the new MF cameras mirrorless. If they were you would have no size increase from current SLR cameras, and using on-sensor focusing would get rid of faulty AF issues, and it would mean wide angle lenses wouldn't need to be retrofocusing.
It would be cool to see if they started with both SLR and mirrorless cameras and an equal set of lenses for both, then the market could decide which system is better.
+1, a MF mirrorless might actually make alot of sense, even more so than an APS-C one. Picture an interchangeable lens Hassleblad SWC with large, (re)moveable LCD. Could be a great landscape/architecture camera.