If you are playing the PlayStation 4 version of the game, you will be able to select one save file to upload to the cloud. Once you launch the PlayStation 5 version, you will then be able to download it. This method allows you to transfer between different devices, doesn’t require a PlayStation Plus subscription and only one save file is supported.
If you are playing on a PlayStation 5 console via backwards compatibility, once you download the next-gen version of the game, your PlayStation 5 will automatically read your save files.
It’s the same thing that Ghost of Tsushima did, you start up the PS4 version, select a save file to (in my words sort of a PreLoad), close the PS4 version, start up the PS5 version and then you will be able to download the PS4 save file into the PS5 version.
The Full patch notes for version 1.5 can be viewed at the Cyberpunk Official website.