I don't see any international ban sticking tbh. If it happened then the majority of best players in the world will play there, and FIFA aren't going to devalue their own tournament. Empty threat imo.
Everyone else other than the breakaway league would have to stay strong and stand together. You never know, some of the best players might want to play in the World Cup and shun the breakaway clubs. I suppose money would talk to a certain extent.
The only way to stop the breakaway league happening is to isolate them completely and make it clear that it's a one way ticket. If not then just accept it as inevitable and let them do it. I think they are the two options.

