Rebels / xxD and EF-S lenses will not "transition" to R mount. they are being *replaced* by EOS-M bodies and EF-M lenses.
i dont think there will ever be Canon APS-C cameras with EOS R mount.
Canon has evidently decided to go with 2 mounts, 2 systems, each perfectly well chosen for the respective image circle:
APS -C = EOS M with EF-M lenses
FF = EOS R with RF lenses
"EOS 7D category" will be replaced by
1. higher-end/faster EOS M top models (APS-C) and even more so by
2. action-capable, hi-rez, well-croppable EOS R bodies )with FF sensor). Canon is just not yet able to fully deliver it (see interviews with EOS R team - sensors (readout speed) and DIGIC are not there yet. They need another generation jump.
PS. hope this qualifies as a "carefully considered" contribution.
mirrorfree cameras can be made any size. M5 is not so different in size to smallest Rebel. If Canon brings an EOS M a bit bigger and higher positioned than M5, it may well be "large enough" to satisfy 80D / 7D users who "don't like things dwarf-sized".
Fullstop, thanks for replying.
I actually wrote: "As the XXXD (Rebel) models are APS-C - I believe we will
not see a 'like for like' transition to R mount. "
Canon M series is not a replacement for XXD & Rebel models ... they are a different market. I own two Canon EOS M bodies (and 5 x EF-M lenses), as well as >3 Canon APS-C DSLRs, and several dedicated EF-S lenses (as well as EF lens, including L glass).
While I believe
in the long run there will be 2 main Canon
mounts (EOS-M and RF), I believe there
may be a market for APS-C bodies (& lenses) which are larger than the current EOS M bodies. The EF-M lenses do not necessarily need to be different (or larger)... With their extensive market research, customer feedback, etc - Canon definitely has a good idea of this.
The ergonomics of my EOS M5 is inferior (and quite a different shooting experience) to my EOS 80D.
Likewise, my EOS M5 (and EOS M10) with small lenses (e.g. 15-45mm or 22mm f/2) is far more portable than even a 100D with EF-S 18-55mm (which I have owned). Horses for courses (many horses, many courses).
The size and handling of a 80D is vastly different to a M5. Even my 700D is quite different to a M5, and notably different to a 100D/200D. This leads to the wide array of market segmentation possibilities. The point I was originally making, is I expect there will be some changes in models, and not a pure 'like for like' from DSLRs to mirrorless, in both APS-C and FF sensor sizes. I think the customers in the market for a "7D" type body in mirrorless form,
will find a model that (mostly) fits their needs, but it may be more different as a mirrorless.
These are exciting times to be a photographer. In any mount, for any sensor size, and in both DSLR and mirrorless markets. Thanks Canon for being a company that develops and delivers great products well, so we (well, many of us) can enjoy capturing images (photos as well as videos) and sharing these with others.
PJ