Disco is most definitely not dead. In fact, if you were to look at relative usage as "dead", and compared Emacs and disco, I'd put money that Emacs is deader than disco.

Disco lives on as house music, which has influenced current pop music so much it's scary. Disco didn't die, it just went underground. Like every other cultural phenomenon, it has its subcultures and offshoots. I could play you music released in the last year that you would probably think was released in the late sixties.