It would not surprise me that they add this and try to one up the Sony A7R5 capability. Canon does care about Megapixels and does not want to be perceived as being behind. This 3X3 IBIS trick is one way to tons of megapixels. It is probably not high on my personal list of needs though.
I want to get rid of the the 30minute timer, operate the ES a speeds slower than 20FPS. (The R7 offers this!!!)
I would like them to unify the auto focus with the R3 and R7 which are very similar and different than the EVF for autofocus in the R5.
Having used a camera that has this feature I can tell you that it looks a lot better on paper than in practice.
Getting good results out of it requires everything to be perfectly still, and even the slightest motion results in some funky graphics.
Also, although I haven't actually run the calculation, I have a strong feeling that at 400mp the lenses available today wouldn't even be able to resolve the image to fine enough detail to matter. But I'm glad they're trying to keep up.
I can believe to get great results you need a great deal of patience and not to mention a solid tripod. I don't know how much increase in detail is possible even with the best of L glass. I will play with it but I doubt I will use it much. Astro may be one application but the earth rotates so it need to have fancy AI tracking correction features built in. Maybe that is the heart of the breakthrough it may demonstrate? The A7R5 apparently does some tracking and correction for movements.
Having used a camera that has this feature I can tell you that it looks a lot better on paper than in practice.
Getting good results out of it requires everything to be perfectly still, and even the slightest motion results in some funky graphics.
Also, although I haven't actually run the calculation, I have a strong feeling that at 400mp the lenses available today wouldn't even be able to resolve the image to fine enough detail to matter. But I'm glad they're trying to keep up.