I wouldn't bet on that. AES and the various public/private key algorithms are well within reach of embedded, low power processors transmitting small amounts of data (i.e. camera/lens protocol). If Canon RF lenses communicate via a high level, serialized channel over the new pins the packets could use strong encryption.
If Canon doesn't etch those keys into the silicon itself, with no read out capability, then they can and will be discovered. But understand hiding the keys on the silicon is not a new thing (Apple's Secure Enclave). So it is possible the RF protocol is out of reach of 3rd party lens makers. I hope Canon is not that short sighted and greedy. But it is a possibility.
I probably missed some earlier posts in regard to this discussion, but isn't the mount distance a problem going RF to EF? Any such adapter would have to include glass to compensate for the back of the lens being so far from the sensor. Doing the glass right so you maintain 90-95% of the original lens IQ would put the price close to the cheaper RF bodies (by the time they appear).