Hard to say
... but I don't see how FB can circumvent the limitations to feed its ML the same user-level data quantity & quality it was using (even though they have users logged-in multiple apps, and the SDK integrated - happy to be challenged on this if detailes are provided), meaning the optimization is very likely to drop in efficiency (leveling playing field with other networks?).
Maybe CPM drop can compensate partly this? But then only for very broad audience products
Maybe targeting will come back in a revival after losing importance in the last 2 years?
+ Adding the same question for UAC, where I can see even more impact due to the nature of the inventory behind.