Well, you are right. No new sensor no new camera. So a big question is how close they are to a new sensor. If Canon does put something out at a higher price point, it will have a new sensor in it, and maybe a pair of Digics. The Tilty/Flippy world likely be the same, and there might or might not be upgrades to the EVF, the touchscreen interface, and DPAF. There might also be a larger body. Timing? Depends on where they are on the sensor.This may very well be the "Flagship" EOS R.
What makes anyone think that Canon has the ability to build a better mirrorless than this in the near future? As far as we know it has their best sensor, best EVF, best touch Tilty/Flippy, best processor, card slot, DPAF etc. Like it or not, this is state of the art Canon mirrorless. What else do they have which they didn't include? A second card slot? It's Canon we're talking about so I wouldn't expect anything better than this for a while.