Don't be surprised...
if Cheney announces he isn't going to run for the VP position again due to health concerns. A nationwide campaign is very stressful.
Besides, it wouldn't be the first time that a President ran for reelection with a different VP. FDR had three different VPs (John Garner, Henry Wallace, and Harry Truman) and Gerald Ford ran for election in 1976 with Bob Dole as his running mate, dropping Nelson Rockefeller.