Most of Horizon Forbidden West's development and playtesting was done with the PS4 in mind, although the PS5 version will have some extra detail.
This is according to a recent interview with Game Informer. When asked about the game's development across the two consoles game director Mathijs de Jonge said, "A lot of the development has taken place on the PlayStation 4 and a lot of playtesting is also done on PlayStation 4. So we are ensuring that owners of that console have a great experience and that the game will look fantastic on that console."
This comment comes after a Q&A with Hermen Hulst revealed that God of War and Gran Turismo 7 would be coming to PS4 as well as PS5. Although Forbidden West has always been said to come to both consoles, the recent interview caused some controversy among PlayStation fans and has brought the subject back into the light.
The most recent gameplay showcase for Forbidden West also spawned a lot of memes about the PS4 fan not being able to handle the graphically intense game, but it looks like development and playtesting were done with the PS4 in mind, so it should be able to handle it.
Mathijs also commented on the PS5 version of the game and what that will bring to the table. He said, "For the PlayStation 5, we can go much further of course visually. We can add a lot more detail, graphically, the rendering technique for the underwater scenes is special on the PlayStation 5. It has extra details and extra systems - the wave technique is better on that system as well. The lighting on Aloy on the PlayStation 5 has much more definition." We also know from recent interviews that the PS5 version of the game will offer a performance mode that keeps everything at 60fps.
These comments should alleviate some of the concerns that Horizon Forbidden West won't be able to run on the older consoles, and that it isn't making the most out of the PS5.