I think it should be technically feasible but i'm wondering what the draw of it would be over just doing more native ports. Many of the console's heavy hitters are already playable on PS5 via BC:
God of War 3 has a PS4 remaster.
Heavy Rain and Beyond have PS4 remasters.
Uncharted has the Nathan Drake Collection PS4 remaster.
Journey and Flower got PS4 remasters.
Demon's Souls has a full blown remake on PS5.
Dark Souls has a PS4 trilogy remaster.
The Last of Us has not only a PS4 remaster but also a PS5 remake.
Red Dead got a PS4 remaster with 4K60fps on PS5.
Ninja Gaiden has the Master Collection for PS4.
Nier got a PS4 remake.
The Resident Evil, DMC and Dragon's Dogma games from the seventh gen all got PS4 ports.
Bayonetta and Vanquish got HD ports.
Yakuza had a PS4 remaster collection and Ishin got remade for PS5.
Metal Gear Solid 4 is likely coming in the Master Collection Vol. 2.
Gran Turismo will never be emulated or ported due to car licensing.
The Killzone, inFamous, Ratchet and Resistance series seem like easy choices for 4K trilogy remasters. Maybe MotorStorm too, although it's quite dated. I'd rather buy a bespoke package of these games than see them emulated.
There are the Bluepoint remasters of God of War and the Team ICO games, but then Sony may likely use their new PS2 emulator for those. I guess one advantage of emulation is that lazy publishers (like Namco with Ridge Racer 7) don't have to put in much work versus porting - but then will Sony want to put in the work building an emulator when so much is already playable?