Map as much osu!stream stuff as possible.
I don't even think that it'd be possible for the game to "go." It's a standalone application, so as long as there are people to map, all that'd be missing is the BSS system and competition. Besides, somebody would make their own tool for rankings and multiplayer, then there are plenty of chat apps to complement the experience. I can imagine somebody making their own osu! forum as well, unless everybody were to pile into Hexis and make its community less elitist.
In a nutshell, I wouldn't worry too much.