A bit early for discussion of the CJFL championshop game, but a date has been set (Nov. 11). Location yet to be determined. The PFC hosted this year, so I'm guessing it'll be BC or Ontario next.
We'll have to wait for the CFL schedule release to see if it's possible to pair the two events, but I suspect not.
I'm not sure if they always rotate like that (even though that would make sense). Maybe BC and Ontario will swap, seeing as how the Grey Cup is in Hamilton in 2023 and Vancouver in 2024.
But yeah, I think you're probably right that the Grey Cup will be a week later. Even so, it might not be a bad idea to host it the week before the Grey Cup. It could add a sprinkle of extra attention/pageantry.