Clubber Lang

So according to Rocky canon Ivan Drago did win the Heavyweight title and retire undefeated, (as a pro. His match with Rocky was, of course, an exhibition,) but whatever happened to Clubber Lang? As champion wouldn't he have been entitled to a rematch and wouldn't
the Rocky/Clubber rubber match have made all the millions?

For that matter what about Tommy "the machine" Gunn? I mean  he was still champion even though Rocky beat him up.

Tommy Gunn was the Billy Gunn of the boxing world.  They probably stripped him of the title after the movie.  
As for Clubber, I can only imagine that he immediately retired and became a motivational speaker.