Has Sony made it available as part of their SDK? They are always very quite about it maybe AMD aren't allowed to talk about it publicly.
They don't have to. FSR 1/2 are open source.
It could be that Sony's SDK already has the code for a temporal reconstruction technique of their own. Insomniac has been developing and implementing their own temporal solution for many years, for example.
I honestly think we won't see many FSR2.0 games, most devs will continue to use either Unreal Engine's TSR or TAAU... or their own engine's up-sampling which are usually either on par with FSR2.0 or better.
UE isn't the only engine around, and even for that it's probably just a toggle like it is for TSR:
We'll need to see performance and quality comparisons on TSR vs. FSR2, but if they trade blows between hardware solutions then I don't see why they wouldn't make it available.
Regardless, due to its free and open source nature I think FSR2 will be made available on many indie to smaller AA titles that use lesser-known engines. Especially as it begins being implemented on consoles.