Your argument rests on one assumption; that mirrorless renders DSLR obsolete... or, to be fair, that mirrorless provides 10 times or more utility that DSLRs. Currently mirrorless does not do that. In fact, mirrorless currently does not beat DSLRs in all aspects. Battery life and the ability to see through the camera when it is off are 2 characteristics.
Doubtless battery technology and electronics advancements will make battery life a moot point in the future. However, that Sony, Panasonic and FujiFilm all don't have credible competitors to DSLR would lead me to believe that Canon will release new DSLR models once the RF push has subsided somewhat.
And looking through an EVF in strong lighting conditions is really unpleasant compared to an OVF. I own the EOS R, and I think it is very good in most ways, but I don’t like using it in strong light. Highlights and shadows does not look natural, and using an EVF in such conditions takes the joy out of photography. I hope the OVF stays for a long time, AND I hope newer DSLRs comes with exchangeable matte screens, such as the 1D series, the 6D, 5D classic and 5DII.