Disco was dance music and that's still around and bigger then ever and definitely bigger than rap ever was or will be. Calvin Harris is my favorite dance music artist right now. He always has multiple hits on the charts including one I can't stop playing right now called
Acceptable In The 80's from his album I Created Disco.
Believe it or not there are some highly evolved rappers who don't resort to degrading vulgar lyrics. Mos Def raps about water conservation and mathematics.
Tricky is probably one of the most sophisticated rappers ever blending rock, hip hop, alternative, jazz, and blues into intelligent hypnotic tracks that are timeless vs. dated like most rap.
Check out
Hell Is Around The Corner by Tricky. The sound will surprise you. His 2010 album Mixed Races is awesome. Sadly there aren't many rappers like these 2.