One feature that hasn't been widely mentioned in the writings I've seen about the Nikon Z7 camera is that Nikon has decided to give photographers a range of aspect ratios, including 1:1 at 5500 by 5500 pixels, which gets me a square format image of a little over 30 megapixels. Oh joy!!! This might be the new camera for the legion of portrait photographers who crave being able to see their format (as it should be) in the high resolution EVF finder of the camera. We'll be able to compose as we did in the halcyon days of image making. No longer enslaved to a paltry couple of lame aspect ratios, or nearly worthless red frame lines overlaid on an optical finder. We'll see the square (I hope) surrounded by a rich field of black and will walk away with files big enough to satisfy most people who want to make large prints.
I haven't check to see if the Canon full frame mirrorless camera offers the same wonderful compositional freedom, but I hope for the sake of Canon shooters that it does.
The lack of a 1:1 format in my Sony A7Rii (when it would have been so incredibly easy to include) is one of the reasons I soured on using the system. True, the D800s don't have a square format or even an EVF but I see the D800s as a stop gap respite in the mad rush to the future. And in my world the future will be square.