Yes, it's going to get ugly, we can count on that. I think Graeme Wood makes a good case for ISIS taking its apocalyptic vision seriously, as difficult as it is for a lot of us, including a lot of Muslims, to get our heads around. Even if some of the deluded fools from North America, Aussie and Europe who realize their mistake would like to run away they will find that very difficult. ISIS relish a fight with the Shia at least as much as they do with us, and in my opinion it is better to let their (nominal) co-religionists sort them out (with indirect support from the west).