Steam version will be removed late 2019 when it releases on the Epic store. It will still be supported, but supported only so if you like a new car or want that new Pass you'll need to switch over to Epic (meaning you lose everything). And with the Epic store, you can't trade so no chance in hell of trading with someone if you've got a cool something they want and they have a cool something you want.
They are trying to walk it back as a lot of the fanbase is pissed over this. Oh don't get me wrong, there are people going "why are you so angry, this can't be anything but good", however a lot of people feel betrayed because they felt like Psyonix was the little Indy that did it. They gave money for keys, passes and stuff because of that.
As for me, I'm probably out. Between this and Gearbox CEO's insane outburst, I don't exactly trust anything Epic.