There is a rumor here of a high end EOS M camera coming at the end of this year, or beginning of the next one. If you have time to wait for this to come around, that's of course better to make decisions around rumors.
I personally don't think that it will have much to do with the 7D II in terms of market segment. The M system is not about large Tele lenses or weather sealing.
I also think it is more likely that the high res R (80 MP+) will be aimed at the guys looking for reach in the RF system than a APS-C R camera. But that is my personal speculation, not based around rumors.
That's why I think if they decide they want the 7D replacement to be on the M mount, they will likely brand it differently. It wouldn't be the M7, but it might be something like the PM7 (P for Pro or Prosumer, though they could pick some other letter, I just had to pick something for my example). It would use the EF-M mount but not be part of the M series. Or they could just say "let's expand what M can mean" and not bother with the distinction.
I expect a very high res R (R5s, R3) like you do (but who knows how soon?); it won't necessarily be marketed
primarily to those folks but just providing a 1.6 as well as maybe an even more extreme (2.0 for a 20+MP cropped picture?) crop mode would definitely be
talking to them. However, many people interested in a 7D replacement won't want to pay that kind of money; I'd expect that camera to cost at least as much as the R5.