Over the past few months, Psyonix has explained how various aspects of the transition to free-to-play will work, including progression across platforms. There will be an update for existing players tomorrow (September 16) allowing them to link the game to an Epic Games account. Once you have done that, you can access Rocket League topics you have unlocked across all platforms. Those who already own the game will also receive Legacy items tomorrow, and the update includes other additions and changes in quality of life.
When Rocket League will be free to play next week, it debuts on the Epic Games Store. If you claim the game there before October 23, you will receive a $ 1
It looks like there is one Fortnite-related in-game event also along the way. Psyonix said it will soon reveal more details about a Llama-Rama event, which starts shortly after the free-to-play move.