Will Canon allow EF lenses to work on future RF bodies?

This idea is ludicrously absurd.

Canon will surely continue to phase out its production of EF lenses and will eventually replace its offerings for which there is not yet an RF successor. The EF 35mm f/1.4 II and 11-24mm f/4, for instance, are still important parts of Canon's professional lens lineup, but RF successors will replace them in due course.

But EF lenses will also surely continue to work on RF bodies. Any notion that they would cease to do so is absurd.

Now, on what basis can I say this?

If you're familiar with the design of the RF mount and RF cameras, you know that the RF mount was specially designed to accommodate backwards compatibility with EF lenses. The EF-RF adapter isn't active, but instead passive, as has been alluded to in this thread, i.e., the camera body itself speaks the EF protocol and the adapter does not need to translate internally. Contrast this with the Nikon FTZ and adapters made for EF lenses onto non-Canon bodies. The RF mount was designed from the ground up for compatibility with EF/EF-S. This is basically just what we call a good design principle. One of Canon's greatest strengths in the DSLR era was the EF lens selection. And the fact that Canon has the most native handling of its DSLR lenses out of the big players is a point in favor of R-series cameras!

The shift from FD to EF isn't really comparable to the shift from EF to RF. Yes, perhaps Canon could have designed the EF system to have a shorter flange distance. But there would have probably been significant compromises attached to doing so. Just take a look at what Nikon did with the F-mount (which became hopelessly fragmented with many different only-sometimes-compatible revisions). The EF mount was designed to get things right the first time and keep them the same way; it was a breaking change meant to prevent future breaking changes. Of course, film bodies in those days weren't really like digital bodies, either, especially if we're talking about manual focus lenses. The comparison is so apples and oranges that it's hard to approach.

With changes such as the hotshoe change here, things break because the actual hardware required changes. Yes, it is somewhat cheaping out on the R50 to require an adapter to use most hotshoe accessories. But it's still a matter of hardware; it's not like there is some artificial software restriction on which speedlight you can use.

The RF mount was designed specifically to be an extension of the EF mount. Blocking EF lenses would be a matter of software, not of hardware.

Canon never blocked an EF lens in firmware. Why would they? All of them going back to the 1980s remain compatible with the latest and greatest cameras. I have personally used some lenses from the late 80s on my R5 before. And more than that, Canon has never disabled third-party lenses through firmware, whether EF or RF. Even the third-party RF lenses that Canon said infringed some patents remain operable with current RF cameras with the latest body firmware, despite occasional hiccups (normal with third-party lenses).

You presume Canon will disable EF support in software on future cameras to prevent the use of third-party lenses. But what about the many professionals who will continue to use EF lenses for decades and decades to come? I'm certain that thirty years from now, EF lenses will still be in use on a daily basis by pros. (Hell, some of them might even be popular as "vintage" lenses!)

This move would make the R5iv or whatever less useful than the R5iii by artificial means. This would be not only a marketing disaster, it would significantly damage the real-world usability of Canon's cameras. And Canon would not benefit at all.

In the future, Canon will do what they've always done: try to convince people of the advantages of the new RF lenses. The later EF lenses have similar advantages over the early entries from the late 80s, too. The RF lenses often make real improvements. But people will remain free to use EF lenses in the future, just as they can use old EF lenses today.

Otherwise, Canon's entire RF design was a waste of their time, and their new cameras will be markedly worse than their old ones!