My thoughts too. I am holding off from purchasing them on the ATV though incase they release a separate 4k version of each film. Very confused about that one. Hoping the PS5 does Atmos too for the reason you stated. I have a few UHD discs that I got free here but no player yet.
Apple do state they will upgrade their films to 4k, I suppose it's more if they can get the rights for this though. While I am sure someone will, it's more likely to be Amazon if it becomes a format war as they have the TV series coming and Amazon personally sucks I find for movies and no dolby vision.
I just don't want to drop £££ until I can find a bit more information on what this 2021 pack will have and likewise if the PS5 will do vision and atmos.
Otherwise I will just buy them bog standard 4k versions and rip them to MKV. Least that way I can play on my nvidia shield with vision and atmos and it won't mean switching disks halfway through the extended versions either.