Publisher NIS America has confirmed that the PS5 version of Ys IX: Monstrum Nox will release on the 9th May in North America, and the 12th May in Europe (as if the first half of the year needed an even busier schedule). Must like the current-gen edition of Ys VIII: Lacrimosa of Dana, it doesn't look like there'll be an upgrade path if you already own the game on PS4, which does put a dampener on things.
The action RPG will still be worth checking out if you're new, though. We reviewed Ys IX back when it first released on PS4, and while we don't think it's quite as sharp as the aforementioned Ys VIII, it's still got some cool ideas and a fantastically fluid combat system.