GT7 will 100% benefit from PSSR 2.0, as Sony is saying it is implemented at the system level through a toggle...
My only concern with this, is that when settings get a toggle like that, there is probably a caveat of your mileage may vary depending on the game lol. But I would expect immediate improvements in GT7.
I would also imagine that there is more to PSSR 2.0 that is developer facing. I would hope that as a major first party studio, that PD would have been one of the first with access to these tools, and that they will natively (in game engine) implement PSSR 2.0 with a patch