The concern would remain even if the language were dead-straight and stated specifically that Rocket League would continue to be available for purchase on Steam in 2020.So nothing has really been confirmed or changed. The concern remains.
Epic feels not the need to hold themselves to their own fucking word.
Epic stans sure don't feel the need to hold Epic to their word, either. Epic could say one thing, do another a few weeks later, and we'd have more than a few posters being like "Wow, 300 IQ epic move, Epic! This will really put the pressure on Steam to develop Half-Life 3!"
So really I've just got concern all-around for Epic because I believe they'll do whatever they like at any time regardless of anything they've ever said