It is certainly an interesting situation. The fact that the 7D II moves lenses suggests that that's what they want out of moving it to the R mount. Canon may need to get more people buying into that system as quick as possible to keep it moving. Canon has aggressively priced the R and RP, likely to get more mounts into the wild which need lenses. I wouldn't be surprised if both the R and RP were loss leaders considering the cost of comparable DSLR release prices in the Canon ecosystem.
Here's an idea - if the spiritual successor to the 7DII was a full frame R camera with a (somewhat) lower resolution sensor, maybe they could release that alongside an EF mount adaptor with a built in teleconverter. The R can focus at f/11, so with a 2x version you could effectively turn the 100-400 into an autofocusing 200-800 on a full frame with improved light collection. Releasing a full frame camera with a somewhat lower resolution to allow a much faster burst rate combined with a EF adapter/teleconverter would could tick a lot of those boxes the 7D II was filling while giving better light collecting power, and provide a better vehicle to move those with interest in crop sensors to move up to full frame and start buying RF glass. Who knows what something like that would cost, but if the 90D is moving up market I would expect the 7D II successor to do the same. Crazy ideas, I know, but if Canon's objective is to get more people buying into RF glass then moving the camera which sells the most glass to the RF mount could be one way to do it!