The problem is how Covid would complicate in releasing these games. Considering that PS5's are still selling out even now and will probably continue to do so until sometime in 2022, I wouldn't be surprised if Sony decided to make the decision in 2022 to port their games to ps4 as well for 2023.
Well Herman did mention that the PS5 exclusives would be technical showcases. With that said Sony still needs more of them throughout the next few years. People still need a reason to upgrade.