RC v1 (for Spigot 1.8-1.12) will lose support once Minecraft 1.17 arrives. If you're currently using it and have experienced any bugs, please let me know so I could fix them in a final update.
RC v2 (for Spigot 1.13-1.16) will only receive bug-fixes after MC 1.17. I don't know how many new features will make it to RC v2 before MC 1.17 arrives, we'll have to wait and see.
RC v3 (for Spigot 1.17+) will become the primary version after MC 1.17. This new version will include some breaking changes to the database structure, and probably to config as well. There will be a converter to help you migrate from RC v2.