Psyonix recently announced you will no longer need to have Playstation Plus or Nintendo Switch Online to play Rocket League when it goes F2P.
Rocket League will be going F2P this summer, the game will remain the same, but the menus will be changed. An update will be rolled out in the following weeks mid-September, and the launch of F2P will soon follow.
You will be able to bring your progress in Rocket League (Inventory, Rocket Pass, and Rank) to any platform it is on using your Epic Games Account.
It will also be available on EGS the same time it launches Free to Play when that happens you will no longer be able to buy Rocket League on Steam.
Steam users will not be left out and will get this update and every update past it for the foreseeable future.