So whilst 8k would be nifty, it's not a requirement. What I think the large sensors are likely going to be utilized for as far as video goes, is some new kind if video sensor stabilization tech that uses that large area real estate to give you a nice stabilized 4k image without cropping the 4k real estate. That I think makes more sense than a7r4 and a92 having 8k video on board. Sony may also have actual purpose built video cameras in plan as well. It's kind of silly to consider this information in the space of only the a7r, a7s and a9.