Since Sony owns the IP of Demon's Souls, I don't entirely see why they couldn't just make their own game. Especially after Demon's Souls Remake by Bluepoint & Japan Studio - they had the gameplay, physics, and graphics engine fully built. Even now, the PS5 Demon's Souls remake is one of the best looking games EVER made. After the huge success of Elden Ring, the DS trilogy, Sekiro, and so on, Sony could've absolutely made more of these.
Would you have wanted to see a Demon's Souls sequel (or perhaps an entire Sony-exclusive series) made by Bluepoint/other PS Studios devs based on the Demon's Souls remake's gameplay?