VHS and DVD rentals didn't replace ownership. They supplemented it. This really wouldn't be very different, I think. Like with movies, people would rent (or stream, in this case) and, if they like them and want to own them, buy them. That may not sound economical, but consider that you could play any game when it's brand new, saving yourself from paying MSRP, and then, in a few years, when you get the itch to play it again and own it, buy it for a fraction of that price, either new or used. You probably wouldn't save anything on the games that you ultimately want to own, but you'd save by not buying, but still getting to play through, all of the rest of the games that you don't like enough to want to own.