There is a dedicated topic on Google’s plans here
It’s been a while since I read those posts but IIRC there is still a lot of guesswork and interpretation and not all details seem to be known/decided yet. For example I saw a screenshot of an app where the dev said that apps of non-verified developers will stop working. This is something I haven’t seen in the sources that were linked. Those only speak of not being able to install via sideloading. For me that doesn’t sound like a reason for the apps to stop working if they were installed before the new rules apply. Sure, Google would have the power to enforce even that. But then we’re back at “not everything is clear yet”.