...if Canon does pre-announce that it will have 24 or 30 or 45 MP or whatever, other brands with higher resolution can control the dialog and it's an uphill battle for Canon once it's released. This way, the actual MP is one part of the entire package of features and capabilities at the time of release, and Canon has more control over the dialog.
I don't really agree with that.
It would be true if there were a long list of features and capabilities to announce, but lately Canon has been previewing those headline grabbing features several months in advance and leaving something like the resolution as the great unknown until the announcement date.
With the 1Dx III, we knew most of the features in advance except the resolution. The resolution was disappointing and dominated a lot of the release chatter.
With the R5, Canon hyped a video spec they couldn't deliver on without massive overheating and that overheating dominated a lot of the release chatter.
Now, with the R3, we know most of the features except the resolution and the underwhelming resolution (if it is 24mp) is likely to dominate a lot of the release chatter.
If I were advising Canon, I would have told them to either leak the resolution of the 1DX III and (if 24mp) R3 out early and take the hit in advance, or hold back on big features like eye-control autofocus and try to bury the resolution in with the discussion of these other features. In the case of the R5, I would have told them not to hype the 8K, but rather emphasize that it can shoot "up to 8K under certain conditions," while hyping features like IBIS and animal eye focus.