I doubt it will ever fade away completely
Ten years from now, even if Iraq has a stable and democratic government, there will probably still be occassional acts of terror. Look at Turkey, or Saudi Arabia. Muslim nations under attack by terrorists.
Settling Saddam's hash would take a lot of steam out of the current attackers, and more importantly, would probably loosen the tongues of a lot of informers who are still nervously sitting on the fence. The object lesson for other dictators wouldn't hurt either.