v4 module series are designed to work togheter without any issue with the v3 series. This said, you do not need to delete the license key from the v3 Core Addon. You can delete the key and the module once you have all products migrated, manually or with the AutoMigrate Tool.
1. Migrate all your products (AutoMigrate) and Configurable Options (AutoAddons)
2. Once everything is ok, delete first the v3 module rcmodsdhosting located in /modules/servers/
3. Goto Addons -> Resellerclub Mods Console section R.S.D.Hosting Module and delete the license key from the v3 Core Addon (Resellerclub Mods Console)
And will this be the same for all v4 modules when they are released?
Yes, all modules will work the same way. You can also operate both modules at the same time. It is however strongly recommended to switch from v3 to v4 to get advantage of all the new features.