Never gonna happen.
ISIS can’t get along with other Islamic terrorists. They are Sunni arabs so Iran has no use for them. Even al Qaeda rejects them. They aren’t capable of organizing anything more than murder, kidnapping and extortion, the latter two being how they raise money. The people they conquer hate them.
Someone may well organize a Caliphate, but it won’t be ISIS.
I just keep seeing parallels between the rise of Nazi Germany and this group.