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

antonio-salieri wrote:

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 fact that they've maintained compatibility with the EF mount across their entire ILC product line for upwards of 35 years speaks to just how well they engineered it.  Yes, EF-M and RF bodies require adapters to mount EF lenses, but that's because of mechanical differences due to flange distance and (in the case of EF-M) mount diameter for the smaller bodies, but the signaling protocol they designed in the 1980's is going strong on cameras they never could have imagined at the time.  There's no evidence that Canon is being held back by either the EF mount or the protocol.  EF lenses if anything work better on RF bodies than on EF ones.

Sometimes breaking compatibility is necessary to move forward.  Those sometimes should be rare, just as it has been.  Nikon tried to maintain compatibility with the F-mount, as you noted, and while it might be possible to mechanically mount a very old lens on a new body, that combination might not be very usable.  That hasn't happened with Canon since the switch.