Square Enix has made it clear that Final Fantasy 7 Remake Intergrade will not be available on PS4. Since a majority of the new content wouldn't be usable by the PS4, this decision makes a lot of sense. ... This doesn't apply to anyone that got the PS4 game when it was free on PS Plus last March, however.
It includes an upgraded version of the original game, plus a new episode featuring Yuffie. The PlayStation 5 game is now available to purchase, but the rollout is bit complicated. It comes in a few different editions, and owners of the PS4 version get some stuff for free.
To upgrade an eligible digital PS4 game you already own to the digital PS5 version:
Sign in to your existing account on your PS5 console.
Find the PS5 game in PlayStation™Store, or by Search, and go to the game hub for the PS5 game.
Select the upgrade offer on the game hub and review the upgrade offer.