There are good reasons for getting rid of the mirror, and good ways to do so now, even if reducing the size of the camera to something pocketable is not part of the goal. MF camera companies ultimately will go to CMOS sensors, the continued lack of which is what blocked many of the other advances in the imaging pipeline that have been happening on 35mm. Once large, relatively economical CMOS sensors are in use, then Live View (which leads to EVF), image stabilization, mirrorless, etc. will follow along just like with the 35mm players. Even video... shocking!
I wouldn't necessarily have thought Hassy would be the first to do this, but somebody will. And the other MF players will follow... at least those who continue to survive. If Pentax put out a mirrorless 645 and had all the other solid qualities of the current 645D, I would go for it asap.