Well, who will the X-Men fight on their secret island?
Themselves?
I mean, yes, that sounds stupid, because it is, but aside from Sentinels and utterly generic groups of mutant-hating humans, the only significant enemies of mutants during the past two decades or so have been OTHER MUTANTS, so once again, all that this really amounts to is a more extreme form of the completely stupid status quo that's already dominated the mutant franchise for a couple of decades by now.