I don't have the numbers and info that Canon marketing has but if I were setting in their meetings I would .
A. Do a 90D or 7Dii type product. Because I think smart phone are killing the low end.
B. Not do an RF-s line of lenses. It confuses people.
While I am not sure about how likely a 7D-type of RF aps-c camera would be, I also don't think that there will be "RF-S" lenses.
There are already RF lenses which require some stretching in post-processing on a full-frame sensor. I wouldn't be surprised if Canon will release further lenses with focal lengths which are kind of typical for aps-c sensors, but which also work on full frame with significant post-processing.
Most of the lenses released so far which fit into that category are rather light and lower-cost, and not that different in terms of size and weight from EF-S lenses. A dedicated set of RF-S lenses would likely have no significant advantage in terms of weight or cost, and wouldn't work on full frame.
Like that Canon could address the low-end full-frame market, and the same lenses would be a still lightweight and cost-effective solution for typical DXX-DXXX customers.
As for the 7D crowd, how many are really using that type of camera with cheaper EF-S lenses? I would guess it's a minority, and that's also why I definitely do not expect to see a 7D-type camera with M-mount.