Stuff like this is bound to start happening eventually. People find disco, play it for some months or years, but eventually it just gets a little old, like anything else, and so people move on.
Also, new games coming out will consistently draw people away as we move on in the future . This server and community is already ~8 years old. That's a pretty long time for any mod.
Do we expect Disco to last 50 years?
It's still here, enjoy it while it is, and remember it fondly when it isn't.