No processor problem anymore .
Its more about read out speed and about how much they can raise megapixel and keep high iso peformance same.
Peoples here say downscaled 5ds high iso resolution is as good as 5div,so not imposible raise megapixels i guess.
and we dont know what new generation sensors can do.
How many M lenses they released this year 0 i believe and 3 RF lense. So if they equally put bigger effort to full frame sensor than to 32mpixel crop sensor,it should be awesome.
m62 does 448 throughput and focus same time , 1dx3 does have extra processor for focusing probably , so with 2 digig 9 i would think throughput is somewhere around 1500.
About missing 6k video. Also possible sensor is too small for 6k could be just 12mpixel, to make possible perfectly working electronic shutter.
Then lame 20fp burst is plausible cause canon just except peoples use video capture for more faster burst.
Sport pictures anyway used on internet so 12mpixel is just big enough.
So my guess for sensor size is 12-80 mpixel
Worst explanation to more worse readout speed than M6ii and no 6k video would be they reuse old 1DX2 sensor
.