There better be an "afterward" for Syria and the Middle East because what we are now experiencing is what happens in absence of an "afterward" to which people can cling with their hopes. The West is now learning the hard way what happens when local problems grow legs and go global, though you would have thought that 9/11 was a clear enough warning. The truth is: Since the fall of the Osmanic Empire almost 100 years ago, the West has had no coherent policy for the Middle East, all we did was carve it up and hope that things would somehow sort themselves out.
The problem is not going to go away, will only exacerbate and if ISIS topples Syria and Iraq, then we will for once have a really working domino theory at our hands, except that it is not in Southeast Asian jungles this time.
And there is no military solution. Only a Marshall Plan for the region on a grand scale will help. Even that won't stop the killing and unrest over night, but it will dry out their sources in the long run. Marshall Plans are cheaper than wars too.