Why don't CaNikon give big, bright 100% magnification OVFs for their top of the line APS-C bodies? That will be a really useful upgrade! Such EVFs are already available from PanyOly and Fuji on their action focused cameras.
Doesn't 7DII have just such an OVF?
100% magnification high quality bright OVF in the form of solid glass polished pentaprism is very costly, requires very precise adjustment during manufacturing process and is heavy. Only top class camera with a price tag to match can have it. The rest will have do with cheap pentaprism and smaller coverage and lower magnification.
In the mirrorless world all of these problems go away. EVF is opto-mechanically trivial, has 100% coverage with no adjustment by definition and brightness is adjusted electronically. Also the mirror dissapears and with it complex separate AF and AE sensors.
This is why we probably won't see 7DII replacement.
Please also note that other technical trade offs have changed. With the elimination of OVF, continued improvement of EVFs, falling prices of sensors and higher density of electronics the price difference in manufacturing an APS-C or full frame body becomes rather small. Hence, I think that the APS-C cameras will slowly fade away.
Around year 2000 there were full frame film SLRs on the market for about $500 for a body.
I think that in about 5-7 years we'll see a return of a full fram, interchangeable lenses camera body for about $500.
By this time the cameras will have electronic shutter. Thus they will no longer have any complex optical or mechanical parts in them except perhaps for sensor stabilisation. It will be all electronics. The only opto-mechanical components of complexity will be in lenses. And we know that electronics can be miniutarised, integrated and manufactured cheaply on automatic production lines. Camera bodies will become cheaper.