That may be the case, but it won't address the fact that ISIS aren't going away. The Iraqi Army don't have the resources or solidarity to crush them in heavily Sunni areas, and even if they make some gains in terms of flushing them out of big cities, they are still going to have to fight an insurgency with fighters who are increasingly hardened and able to use all of Anbar and across the Syrian border to regroup. The long term solution is a complete rethink of the political and security landscape in Iraq, involving new elections, and probably an international peacekeeping force to create humanitarian corridors (beyond just Kurdistan) where citizens can live without fear of being murdered by insurgents. An international, UN approved force would be ideal to the US or Iran (or both) coming back in as it would only exacerbate the sectarian divide.