They will simply kill off last gen versions like Gotham Knights did. Sony's made several games that are PS5 only but they feel rooted in last gen design/visuals like Deathloop, TLOU, Returnal and Ghostwire. By the time this game releases in 2025, yeah, the install base will be strong, but if Jason is right, and he typically is, this game that started development in 2014 was not targeting next gen SSDs and CPUs.
I hope Im wrong, and they rebooted the game after shipping RDR2 to target next gen consoles, but Ive been right a lot lately and literally every worst case scenario has come true so im not too hopeful about Rockstar making the right decisions here.