The new generation of consoles is in full swing, and the Xbox Series S and X seem to have gotten really good third-party support with improvements across the board for the most popular games. But not with Rocket League. Despite being one of the most popular games, it is only getting a somewhat better stable frame rate and also loads faster.
Fortunately, it won't stay like this for very long, as Psyonix now has shared all the details for next-generation and it seems like owners of Microsoft's console are really being treated when the update launches in December. Xbox Series X will run the game in 4K and 60fps with HDR, and if you do not have a 4K screen, you'll get it supersampled to 1080p for massive quality improvements.
But it gets better. There will also be a performance mode running in 2688 x 1512 (70% of 4K) with 120fps and HDR. The UI will still be in 4K though. Even the performance mode can be played supersampled to 1080p. Xbox Series S on the other hand plays Rocket League with 1080p resolution at 60fps and HDR. The performance mode runs the game in 1344 x 756 (70% of Full 1080p), but in 120fps with HDR.
Unfortunately, just as it was the case with Star Wars: Squadrons, the Playstation 5 will run the game as it played on PlayStation 4 Pro. This means 4K resolution (checkerboard) at 60fps.