Sucker Punch was already seen hiring developers for a Ghost of Tsushima successor, but this is the first confirmation of the game for PS5.
On their official website, Sucker Punch has posted various job openings for their new project. Reading through them makes it clear that at the very least, they are working on a successor to Ghost of Tsushima which is their most successful game to date. It is also natural to assume them working on a sequel or successor considering the value of this IP.
Now the first indication that they are working on Ghost of Tsushima for PS5 comes from the Linkedin profile of Cinematic Creative Director at Sucker Punch, Dave Molloy. He has worked at Sucker Punch for more than 10 years, so is a senior there in term of experience.
In his profile, Dave mentions that he is currently working on a “Ghost of Tsushima game” for the PS5. Sucker Punch has already released an update that has added PS5 support for Ghost of Tsushima, albeit this works in the backward compatibility mode so it is not a native PS5 version. Based on this fact, we can assume that this is likely a new project unless they are spending time working on a native port for the PS5.
As for the current version of the game, while it runs at 4K with 60 FPS support on the PS5, there are no visual enhancements offered for the PS5 hardware. The game already looks good enough, so the next logical step would be to work on a sequel and get it out as soon as possible, and this appears to be the case based on the job openings currently at Sucker Punch.