The latest Nioh 2 update adds cross-save support for PS5.
As Team Ninja explained in the full patch notes, update 1.24 added cross-save management to the options menu of Nioh 2. You can access this via the system tab on the title screen. From there, upload your PS4 data, then boot the game up on PS5 and redownload your save using the same PlayStation Network account.
The actual cross-save process is pretty straightforward, but there are two minor footnotes here. Firstly, because trophies are handled differently on PS5, Team Ninja says that "some trophies that have already been earned (those that are difficult to earn again) will be automatically acquired when the save data is loaded." Similarly, because matchmaking works differently on PS5, you won't be able to match up via your friend list and will instead need to use a specific password to join a friend.
This update comes just four days ahead of the release of The Nioh Collection on PS5, which bundles together Nioh Remastered, Nioh 2 Remastered, and all of the DLC for both games in a next-gen package with a fresh coat of paint. If you already own Nioh 2 or any of its DLCs on PS4, you'll be able to upgrade to the PS5 versions for free when the collection launches February 5.
While there are no immediate plans for a Nioh 3, Team Ninja says it will announce several new projects in 2021, and Nioh director Fumihiko Yasuda is hoping to take a stab at an open-world game this generation.