Iran is the root of it now. Destruction of Iran would do the trick. A totally destructive victory against a major Islamic entity is required to make Islam go dormant for a generation or a century. Destroying Iran would be too bad from an Archaeological point of view and in considering that mush of the population, the educated portion, would be on our side but it would have to be total. Mussulmans the world over have to believe that Allah is not on their side right now and that is the only way it has worked in the past. Even better would be such a defeat and then colonization of the Moslem areas and forced conversion of the population to something other than Islam. That does work, not on the converted generation but on their progeny. There are Spanish in our southwst with faint cultural memories of their Jewish forebears but they are not Jewish. Spain has many such and families with faint Mohammedan cultural memories and hints of pracitices but they are not Moslems.
You said it best.
Guys Iran is not behind ISIS. ISIS is (mostly) Sunni, Iran is (mostly) Shiite.