We now know that Persona 5 R is a game that will (at least) come to PS4, and it looks like it'll be an upgraded version of P5. But we'll know more in March.
http://gamrconnect.vgchartz.com/thread.php?id=238820
As for Persona 5 S, it could be this?
It's a follow up anime that will air in March. The speculation is that it will cover the end portion of the game.
https://personacentral.com/persona-5-the-animation-stars-and-ours-to-air-in-march-2019/