Given the migration path Canon hasn't provided, your argument backs up my suspicion they made the wrong call.
No, it doesn't. As I stated, Nikon had that migration path. The point is that the vast majority of APS-C DSLR buyers were of the sort who bought a Rebel/xxxD body with a kit lens (or two-lens kit), and that's all they bought unless or until their camera broke, then they replaced it with the current equivalent product. That market segment has shrunk, but those are the people buying an EOS M body with a kit lens and nothing else, and that remains the largest segment of ILC buyers (note that largest segment doesn't necessarily equate with greatest profitability, that is a numbers game involving unit sold and cost of goods).
Those buyers who want to upgrade to FF will need a different standard lens to go with their better camera, so mount compatibility is not really a big impediment, except for those who really can't afford a FF camera setup...and as I said, those customers are not of high value to Canon.
You seem to forget what a quantum leap the all-electronic EF mount was, and may not have been around while Canon shooters were dismayed that their entire outfit was outdated at the stroke of a pen. Even in the mid-90s, 8 years later, I met photogs that said they felt raped by Canon and moved from FD not to EF but to Nikon in response.
So in your mind, Canon's introduction of autofocus and electronic aperture control in a new mount was a quantum leap, but Nikon's addition of autofocus and electronic aperture control to the existing F-mount was not? Your username may be SwissFrank, but your logic has more holes than a wheel of Emmental.
And yet the superiority of the mount made it ultimately worth it, as Canon's share of the pro market went from 25% to 90% if I recall correctly.
Thanks for substantiating my point. Canon made a change to a new mount, incompatible with the previous one, and succeeded. The RF mount is a new FF MILC mount, incompatible with the previous APS-C MILC mount, but you're arguing that's a mistake. More of that Swiss cheese logic.
In contrast there's no corresponding compelling technical reason to move from EF-M to RF mounts, when the EF-M mount could have BEEN the RF mount. And yet we have endless speculation on this very forum of Canon releasing small-sensor RF cameras that would be nothing more than M cameras with an extra couple mm of film-to-flange.
The M lenses are a uniform diameter, and the mount is optimized for a small camera/lens combination. As I stated, making it bigger is contrary to Canon's stated design philosophy for the M line – in which small size is a very large part.
I'm not positive but I think I've seen at least a few Canon patents of lenses with the RF film-to-flange distance but small-sensor image circles.
Time will tell. If Canon introduces a small-sensor RF body, that will prove me right and prove you wrong. Especially if they discontinue the EF-M product line at that time.
Launching an APS-C EOS R will not prove you right. The R line is targeted at high-end buyers, and some of them may be interested in a 7-series approach to 'more reach' (the fallaciousness of that argument did not stop people here claiming the 7DII has more reach than the 5Ds because the former is APS-C). If they launch an APS-C EOS R, they'll launch an RF-S 17/18-xx kit lens with it, and an RF-S 10/11-xx UWA zoom, too. But unless they're going to sell an APS-C EOS R + lens kit for <$1,000, it is absolutely not a replacement for the EOS M. Only replacing the EOS M line with a similarly inexpensive EOS R APS-C lineup would prove you right. Don't hold your breath.
> People are dying to buy lenses? If so, an incompatible mount means Canon sells one more lens.
No, because even with compatible mounts, they'd sell another lens anyway. So the incompatible mount doesn't give Canon a NET sale, rather only a sale they'd have gotten anyway.
So if they'd have gotten the lens sale anyway, why make the mounts compatible? Consider it from the other perspective – Canon sells you a FF body and says you can use your APS-C lenses on it, you do and you aren't happy with the results, so you abandon the system.
> Your suggestion that the EF-M mount could have been bigger to match future RF would mean bigger M bodies and bigger M lenses.
Which lens? Which body? How much bigger? At what cost to sales? You may be right, but give me details on this if you're calling me a liar in front of the world.
If you increase flange focal distance by 10%, you're going to have a thicker camera. The EF-M mount has a 47mm throat diameter, the RF mount has a 54 mm throat diameter. Look at the M2, where the distance from the edge of the mount to the edge of the camera is ~2mm at the top and <1mm at the bottom, and tell me that increasing the throat diameter by 7mm would not increase the size of the camera. All of the EF-M lenses have a uniform 60.9mm diameter. Making the mount bigger would necessitate bigger lenses. Canon cann'a change the laws of physics. I didn't think spelling out these details was necessary for you to understand that a bigger mount means bigger cameras and lenses, but I was wrong.
How can anyone provide details on lost sales for the path not taken? But as I stated, Canon said small size is a big part of the M design philosophy, and bigger bodies and lenses are counter to that philosophy, which is reason enough to make the choices Canon made. Choices which gave them the #1 APS-C MILC lineup.
@SwissFrank Why is it that you continue ignoring the main point, which is the data-driven counter to your baseless claim that Canon gave no thought to the EF-M vs. RF mount designs? I suppose because you have realized you're wrong but are unable to admit it. Sad.