And think about mutants reverting to type.
Apocalypse is all 'Survival of The Fittest'. Without humans as a threat he would go back to that pitting them against each other.
Mister Sinister would probably be trying to continue his research in secret...or not so much secret since there are no exterior threats and he would be found out.
The Shaw's and the Frost's are all about their money and luxuries. In a new society would that even matter? Sure they may make a form of currency for trade among themselves...but what would Emma do without her 5 star restaurants and shopping trips to Paris?
Good point, especially about Apocalypse, since he usually has about as much contempt for mutants with "weak" or "useless" powers/mutations as he does for baseline humans. As for the Hellfire Club's erstwhile Inner Circle, it would be morbidly amusing to see a mutant proletariat uprising in light of how much the Inner Circle has arguably sold out or exploited even fellow mutants that weren't wealthy and powerful for its own benefit. Chickens coming home to roost, as it were.
The spider is always on the hunt.