I think it is a bit of overstatement to say that "Canon" has said there will be no M5 II. One US Canon rep suggested there wouldn't be and in the next breath said the M5 is the top of the M line. I can't find anywhere else in the world that a Canon rep has denied the possibility of an M5 II. It is quite possible that the US rep simply mean there was no M5 II in the immediate future. That said, numbers are cheap, so who knows what will transpire with time and a lower power Digic 9. The M6 II is clearly crippled by the power consumption of the Digic 8 (no 4k crop mode), so there will be future opportunities for new models.Understanding that Canon has said that there will be no EOS M5 Mk II, it seems to me that "parts bin engineering" could make another approach possible. They could put the sensor and lens mount from the M6 Mk II in an EOS R body.
Pros as compared to EOS M6 Mk II: Built-in EVF. Better battery life and compatibility with a wide range of higher-end models. Better handling for larger hands and larger EF-S and EF lenses. More versatile flippy screen instead of just a tilty one. Compatibility with EOS R accessories (battery grip, etc.)
Cons as compared to EOS M6 Mk II: Larger. Heavier. More expensive.
Differences as compared to EOS R: Slightly better resolution. Native access to EF-M lenses. Adapted access (with full resolution) to EF-S lenses. Adapted access to EF lenses. No access to RF lenses.
Of course, if they really want to shake things up (or rather, reduce the amount of shaking), they could use the extra space from the smaller sensor to include IBIS. That is not likely to happen until IBIS becomes available at the high end (1D series and some upcoming R model), but at that point there would be nothing from a technical or marketing perspective that would make it impossible.