As some have mentioned, it certainly makes a lot more sense in the long run, if all the Canon ILMCs had the same mount. So if Canon can make APS-C bodies and lenses that are similar in size and weight to the M line, then it will probably happen. If it does, it will be pretty seamless in my opinion.
As usual, the folks on this forum are forgetting the M target consumer. When their M50 or M6 II is no longer working, or they are looking to replace it in 5-10 years, they will go to Best Buy or look online, and they will see if there is a Canon camera that is similar to their M. They won't care what it is called, they probably won't care if it is APS-C or FF, they will want one of the the smallest, inexpensive Canon models. If they say to the salesman, I only want the body, I already have a lens or two, the salesman will let them know that their M lenses will no longer work on the camera...but, here is the kit with lens for only $150 dollars more. OK, deal done.
Yes, I understand that having lenses that will no longer work if the line is discontinued will be annoying (as an Olympus M4/3 owner, the future of my camera and lenses is up in the air), but generally speaking, M owners will have paid well under $1000 for all of their lenses and will have gotten many years use out of them. If this had happened to the EF lenses, where a typical user may have spent many thousands of dollars on lenses, the loss would be substantial. The M target consumer - in the majority of cases - may never have bought anyhting but the kit lens. Not a great loss.