I think the likelihood is that either Iraq will descend into a Yugoslavia-type maelstrom with much death and destruction and a break-up into mini-states as a result; or it will descend into a Lebanon-type maelstrom with much death and destruction but manage to come back together as a weak nation-state in the end. The second is the better outcome for the region and the world, but it is not guaranteed. Both scenarios are dire, and could spin out of control into regional conflagration.