One factor we won't know for a while is what sort of "real" price the lenses will get, once supply constraints ease. It may make sense for Canon to have a very high suggested retail price at a time when shortages allow it to sell at exaggerated prices, which could then be converted to perpetual discounts later. The "real" price for the 600mm f/4 II was closer to $11.5k new (vs $13k list) in the US prior to the Mark III being released. Perhaps the real price for the 800 f/8 will be $14k rather than $17k once the parts shortages ease.
The advantage of putting out effectively-teleconverted older lenses is probably production efficiencies. This would work great for a company whose strategy is to gain share based in part on price. But Canon hasn't acted like a company trying to drive prices down (costs, yes).
This leads us to a showdown of sorts. Assuming that the MTF charts are somewhat accurate, knowledgeable supertele buyers aren't going to pay an extra $5-$7k for a less flexible lens of same or lower image quality. Most people dropping ~$15k on a lens are knowledgeable. Maybe nuts, but knowledgeable, usually. Which means one of the following are true:
1 - These will sit on the price lists to flesh out the comprehensiveness of the RF line, but won't be actually bought/used much
2 - Canon will lower the prices significantly
3 - There is some sort of special image quality magic that makes these better than teleconverted lenses, and we're all a bunch of geeks jumping to early conclusions
I'm betting on #2 for now. I think Canon sees a small market where people don't like using adapters and/or teleconverters, and they're ripe for exploitation, and then they'll lower prices eventually to make the comparison versus the base lenses less dramatic.