This is a terrible analogy. Rocket League will still continue to be supported on Steam including new DLC released, just no longer sold to new customers. Nobody is taking anything from you.
And they will continue to support linux as well? I find it terribly hard to believe that they will continue to actively develop their linux client to keep up with future DLC after moving the game to an ecosystem that doesn't support linux.
Stop defending these companies. You are entitled to ownership of something you paid for. It’s not a one-time lease agreement no matter what the software companies want you to think.
I'm not sure you read my comment before responding. You retain your copy of Rocket League and it's supported indefinitely on Steam. Nothing has changed for existing owners.