Originally posted by northcoastgreg Actually, MF has the least to gain, because right now it is a format almost exclusively determined by the lenses, all of which require a large camera. The 645D was introduced for people who already owned MF glass. That's why it could be introduced with so few new lenses, and Pentax could get away with very slow release cycle. In any case, if you introduced a new mirrorless 645D system, most existing 645 users would find it less costly just to move on to that far more versatile system camera, the Nikon D800.
It would not be targeting existing 645 users. Pentax only has 1.5% market share. If they want to grow they need to produce products that will attract new users, not appease the 1.5% who already buy.
New mount and new MF mirrorless body that will appeal to new users who wish to move up to MF. MF doesn't need dozens of lenses. I have 5 for my Contax 645 and I only really use 2 of them with the 80mm being by far the most used. I picked up several once people started dumping Contax gear, and now it has gone back up in value as there has been a revival of MF film among wedding togs.
Half of the camera size is the mirror-box and the huge OVF. Pentax could produce a mirrorless MF that would be the size of a normal DSLR.