Regarding sensor sizes, digital tech has pretty much destroyed any concept of bigger = better, a mere rollout of a new feature on one camera and a 35mm sensor performs on par with a larger one, next few years it's the opposite again as scaling catches up. I wonder how much sense it makes to continue to talk about sensor size like it actually matters anymore, performance wise...
If BSI turns out to be the magic bullet a lot of people are making it out to be right now, does Sony even need a camera with the 33x44 sensor in it, if it'll end up performing about the same as the A7RII? If it achieves performance parity, then it would render the MF option a novelty, at least until BSI makes it into medium format.