According to a current report from Ubisoft, Assassin's Creed: Valhalla, release on November 10, 2020, will not only run in 4K on the PS5, but also with 60 frames. And full 4K resolution, as you emphasize, which you can expect. The days of checkerboard 4K should be over for now. Although, there is always a balance between resolution, frames, how nice the game is and how stupid - or not even stupid - the AI. Based on what has been played, the AI seems to be on the usual level and even if Valhalla is optically a small jump to the predecessor Origins in places, there should still be enough of the new console power left to be able to present everything here in 4K60. Meanwhile, every TV buyer in recent years has a 4K TV.
Assassin's Creed is said to draw further advantages on the PS5 from the fast SSD technology to shorten loading times and the Tempest Engine for better sound. So no big surprises, it would be bad if not.