As a 7D MkII shooter I thought I would move to mirrorless when an R7 was announced. Having watched the development of the R ecosystem, I am getting more convinced that will not happen for some time, if ever.
As people keep saying there are 3 drivers for crop cameras: size/weight, cost & reach.
Size/Weight: Canon are still focussing most if not all their R&D effort into expanding the line-up of RF lenses and bodies. Clearly focussing on the items with the highest demand (and they hope profit). In time, once this line-up is near completion, they might start looking at something like RF-S. Until then, they will keep the M series ticking over for this segment.
Cost: Where will this cost saving come from? Smaller mirror (oh, no it is mirrorless)? Smaller pentaprism (oh no it has EVF)? That leaves a smaller mechanical shutter and sensor. Fast APS-C shutters are cheaper than a FF one with the same FPS (less material to move at speed), but with very high speed electronic shutters, this cost advantage diminishes. That just leaves the reduced cost of the sensor. Anyone have any evidence that an APS-C sensor is $1,000s cheaper than FF, rather than $100s or even $10s? The only way to make substantial cost savings is to drop or reduce features. Do you need an EVF? Do you need a rear screen? Do you need a mechanical shutter? Do you need AI AF? Do you need high FPS? Do you need a high res, high refresh EVF? Do you need high MP?
Reach: I love the 7D for the extra reach (which was much cheaper and lighter than a 600mm/F4 lens). But Canon have now given us an R5 with 1.5x reach of an 7dMkII. They have given us a 100-500mm RF that has 1.25x reach of a 100-400mm EF. R bodies focus with smaller apertures than the 7D, so a 1.4x or 2x TC works better on them. They have given us a cheap 800mm lens. Is that not enough reach?
I would still love a unicorn, a small, cheap, long reach R7, but I don't see it happening for a long time, if ever. Unless, of course, the marker research reveals there is sufficient demand for a full featured $4-5K (or reduced feature $2K) crop body, with no extra supporting lenses, which would the appear ~2023/4 after sufficient R&D time. More likely is in 5 years, once the R series is fully established, however by then the market may have changed. Or, Canon may have added some other new feature to their FF cameras, meaning the demand for crop is even less.