Is there a PlayStation purchase or upgrade path?
There is no verified PS5 product, PS4 product, PlayStation release date or price for this title in the checked store. A native PS5 edition, a PS4 game running on PS5, an upgrade and PlayStation Plus access are different routes; each would require its own game-specific listing or announcement. Steam's mention of USB DualShock controller support concerns the PC version and grants no PlayStation licence.
For a PS5-only player, wait for the developer or PlayStation Store to identify an exact edition before expecting a download, upgrade or subscription route. For a Windows-PC player, the actionable official page is Steam, where the game can currently be wishlisted. The release-date page explains why no launch day can yet be put on a calendar.