They are clearly going after the Canikon users with that move. But then, if they are producing lenses that are slightly bigger and slightly heavier than their Canon counterpart, I don't get it !
Why not just keep the A-mount and design a mirrorless body for that mount ?
They had designed a wonderful small body with the A7 first version. They should have kept that logic and produced a set of light sharp lenses to make a small and light system with excellent lenses. Something like a digital M for travel and reportage photography. And have a second line of bigger bodies for those needing fast and heavy lenses. Was it not possible to make a mirrorless body in a shape like the A99 A900 ? I think that a mirrorless A99 would have been just as able as, or even better able than an A7r2 to hunt Canikon customers.
As is, they are going to face some technical challenges due to the size of the body (heat dissipation, ergonomics, not to speak of the short flange distance complicating things for lenses) and the day Canikon awake and produce mirrorless bodies in their usual camera shapes polished ergonomics, the Sony FF mirrorless may explode in their hands. Sony seems to abandon its A-mount, but that seems a bad move to me. The E-mount has both a too short flange and a too small diameter. That will uselessly complicate the design of lenses with zero advantages in return, since now their lenses are as big as those of Canikon.
Retrospectively I think that the introducing of the FF FE mount has not been well thought and they are developing their different camerasystem lines erratically.
I love my A7r and got accustomed to the bigger A7rII, but I'm not happy with the lenses coming out for that system. The A7r and r2 are little gems of cameras but I want lenses tailored for that.