For example, a band like Joy Division. Two masterpiece albums in the form of Unknown Pleasures and Closer, and the untimely death of Ian Curtis cut it all short. They were even heading into the direction that New Order eventually went in, and it would have been interesting to see what Ian Curtis would have done if they fully made the leap into electronic music while he was still alive.
Death
I would love to hear the songs Chuck would have written about the current state of the world. Stuff like 1,000 Eyes always gets me when I hear it today.