Yeah, it’s a moving target for sure. For now, the devs seem to be very certain that AOSP will stay and that they will still be able to port GOS on new devices (although it will take more time and work).

If app installation is not managed by Google (i.e. if you’re not using Google Mobile Services or GMS), Google cannot block the installation of any apps. Graphene’s devs have confirmed themselves that this new measure will not affect their ROM

It does not block anything by itself. I use Adguard as my DNS provider and it does that system-wide. It you can also use a VPN provider such as ProtonVPN that does it

I’ll happily continue using my GrapheneOS Pixel since nothing will change for 3d-party ROMs :)