Play Integrity
• Don't jump the gun before we even know anything. This conversation has already happened 20 times over the years and too many people that don't know what they are talking about speculate and spread around misinformation. It was always going to get to a point where it wouldn't be possible anymore, but we don't even know if that point is here yet.
• Custom ROMs do not rely on play integrity and you can still install custom ROMs with or without gapps and use them as normal, for the most part. Lineage OS and Graphene OS are prime examples of this. Only a few apps in comparison to the whole range available will not work, such as banking apps, wireless payment apps and some games. Also, RCS may not work.
• That is it. There's nothing new, it happens and it will continue to happen until it simply isn't possible anymore. If you rely on play integrity for any of the reasons above then GO BACK TO STOCK AND LOCK THE BOOTLOADER!