I think that, since the EF era, photography has changed, and especially NUMBERS in photography has changed.
I don't have precise numbers and don't want to search them, but I saw them many times, shall we say "camera/lens market today is like 5/10% of what was 20 years ago"? Maybe even 15/20%? Or less then 5%? Well, I feel it's the same.
- Way less people buy ILC and relative lenses, accessories, etc
- Fixed focals were used both for brightness/fast shutter needs (400iso was already "medium-high iso", at least with colours) and quality; but today iso are on a very different scale and 1600iso are cleaner then 400iso film (so at least 2 stop difference; given the same shutter, what you shot at f1.4 in film era you can now shoot at f2.8 of course not accounting the DoF difference), and zooms reaches, and sometimes surpasses, the quality of a prime, also becoming brighter (we all know about the RF 28-70 f2 L)
Introduction to say what? To say that I don't really think we will ever see a 28 L (or a 28 prime of any aperture fwiw), as we don't ever saw it even in EF lineup, and that the RF 24 L and 35 L are not priorities for Canon; I don't think we'll see so many RF primes as we saw in EF era, for all the reasons explained above, there's not that wide market anymore, especially between amateurs and general public (while pro's, semi pro's, content creators etc etc are WAY MORE then in the past), and super bright lenses are not "needed" anymore due to the iso performance of modern sensors. Yes, I know, DoF, gain stops with the shutter at high iso, etc; but surely before a bright lens was much more a "technical need" then today.
Also, for now, they have already covered 24 and 35 with the RF STM versions, and there are pretty recent EF L versions if you really need one bright copy right now. So they don't have any rush for the RF L versions.
I think Canon won't release so may primes as before, and so many BRIGHT primes as before; probably that will be bread and butter of third party manufacturers when Canon will licence the RF autofocus mount.
I think Canon strategy will be to release few, but super quality, primes (as they're already doing), and then leave gaps they don't want to fill (like the 28mm gap) and will let Sigma and Tamron fill those gaps, where Canon is not losing money because they don't have competitive lenses.
So I'm not sure that when they will licence, they will give an open licence; I think they'll licence specific focals and/or brightness to be filled, to have full control of the competition. I don't see Canon giving licence for a competing 50 f1.2 and tbh I don't know if they'll licence even a 50 f1.4 as surely Sigma could manufacture one that would be on par, or better, then the L version but for half of the price, and so even with the 1/3rd stop difference, would be very hard to Canon to sell many others 50mm L.
Otherwise we'll see much more zooms, in general, and much more zooms in lieu of the primes (see the recent CR news about the RF 100-300 vs a new RF 300 prime), and much brighter zooms (others will release stuff like the RF 28-70mf2 L), but also much DARKER zoom, for the very same reason of high iso efficiency. Canon already released some horribly dark RF zooms, I'm sure we'll see many more of them in the coming years.