I don't think it'll be an issue of if he can play at a high level.
The issues will be 1) If he wants to. 2) Do the Rams want to pay him another contract. 3) Do the Rams go after another FA vet QB or do they go all in for a college guy they love. 4) Does his health hold out.

Lot of moving pieces.

He's a clean liver. He seems to still be enthusiastic. He doesn't seem to have lost anything in his arm. His legs are holding up.
My guess is that he stays in the league even beyond 3 more years.