From the article:
Want to play low-gravity “Moonball” with extra boost? It’s possible! Want to relive classic Supersonic Acrobatic Rocket-Powered Battle-Cars game modes like “Cubic” and “Time Warp?” You can!
Whatever your preference, you’ll be able to find your favorite gameplay combinations in just a few short weeks from now when Mutators invade Rocket League! Once they arrive, you’ll be able to create new Custom Matches with the rules and settings made especially from your tastes, while our sweet “Mutator Mashup” playlist allows you to enjoy pre-determined weirdo matches in public games like you’ve never seen them before.