We can verify that Rocket League may be moving to RL Items  Unreal Engine 5, as per a Psyonix activity posting that leaked lower back in August 2021.

The task posting become a piece of a stunning revelation, after months of Psyonix remaining tight-lipped on the opportunity of Rocket League transferring to the advanced engine. Rocket League and Psyonix had simply been sold by means of Epic Games, so it turned into anticipated by means of many who such an statement might have come soon after the game's free-to-play shift in 2020.

"The advertising and marketing branch maintains to construct out its team for you to Rocket League Items Shop  hold and expand its capability to help Rocket League's ongoing projects, as well as destiny Psyonix tasks such as Rocket league: Sideswipe and Rocket League's circulate to UE5. The function might create a committed useful resource to all copy and messaging improvement desires inside the marketing branch." — Excerpt from Psyonix's Job Posting