The headline says it all, really. It's as simple as that. Released a few years ago to both critical and commercial success, Psyonix have gone on record to say that expecting a sequel to Rocket League is futile given the nature of the game.
Being a simple enough idea about rocket-propelled cars driving - and flying - around several gorgeous arena trying to bash a giant ball into the nets of the opposing team, it's the game's bizarre, familiar and easy to grasp formula that brought so many on board in the first place.
During an interview with Kinda Funny Games, Jeremy Dunham, Vice President of Psyonix said: "Why would we want to take this huge community that we’ve already built, that’s still growing, and say, ‘What you’re playing now is going to be irrelevant in 12 months?’ Our goal was to keep making Rocket League better and better so that we don’t lose any of the people that want to play.”
And he's absolutely right. Lightning wouldn't strike twice with this one. Racking up 29 million registered users throughout its lifetime with millions jumping on board in the first few weeks, Rocket League was a runaway success that caught the developers way off guard. Resulting in widespread server issues early on, nobody expected the numbers to climb as fast as they did.
But there's really no reason to even attempt a second release. Rocket League is still getting regular feature updates with cars, cosmetics, arenas and gamemodes already looks incredible with Unreal Engine 3. Sure, there's UE4 now, but there's no point risking a hardware gap that could separate players further.