I think we've gotten used to a pretty slim and trim product lineup, at least where full-frame cameras are concerned. It used to pretty much just be the 1D, 5D, and 6D. Now we have no less than five bodies - the R3, R5, R6, R, and RP - covering a much broader spectrum of feature sets and shooting styles. And the top end of the product lineup is still not fully fleshed out, with the rumored R1 and a high megapixel body still in the works. Some might call that a scattershot approach, but I don't think it's accidental. I can go to Sony's website and select from no less than 12 different full frame body options. Similarly, Nikon rosters six different full frame camera options in its Z line. In both cases, this includes models that have been superseded by newer versions and are still for sale. But I think y'all get the point. I think that the market has evolved quite significantly, and Canon and other companies seem to be doing a good job of evolving with it.
Canon's lineup seems really firm and clearly delineated, even if their numbering scheme doesn't. And while we know that the R1 and a high mpx body are coming at some point, there is little doubt that the R and RP are long enough in the tooth that they could stand replacement. The R name probably needs to go. If not for any other reason than because everything is an R now. You can still make a case for the RP name, based on Canon's historic use of the "Populaire" name and trim level for its entry level cameras. The EOS RP isn't even Canon's first RP. That honor belongs to the Canonflex RP of the late 1950's. I'd like to see that trend continue with an eventual RPmkII. Based on that, the R8 name for the next step up and the R's replacement makes more sense. That is of course my own $0.02, cash value may vary.