Besides any crops or resolution/framerate limitations (or overheating...would they dare?!), usually the AF and IBIS (not applicable in this case) aren't as good as the higher models. But on the note of AF, I have a Canon R10 and I am really impressed with its AF for less than $1K so maybe that's behind us now.
For video, besides possibly having better/more video tools (and external RAW/IBIS/etc), the R6 II may still have better fine detail and IQ (but also probably not enough for anyone to really care).
R7 will also have the IBIS/etc, and 32MP for stills.
Did they say the R8 will have 10-bit? Could be a 'got-ya' but probably not.
It's always a trade-off...you take this, I'll take that. I'll remove this, you remove that...voila, we now have multiple cameras for sale.
No info on the 10bit yet. The R10 got my attention but I have a problem with the crop especially that it's already a cropped sensor. Otherwise I would get one.

