I think I have read somewhere that making a new camera-model is a 18-24 months process. Of course it is a bit blurry when exact the process for a specific model starts, but considering additinal delays by COVID, I cannot image this being a "reaction to market" reaction after the R5 release.
"Fun fact": Around New Year 2019
Imaging Resource had a talk with Canon were they told they had "an 8K video capable camera is already in our EOS R-series roadmap". That must have been the R5, which, as far as I remember, started shipping in late(?) summer 2020.