In the short term, the greatest risk in Iraq is that the country spirals into a more dire state of chaos. This would make the transition to democracy less likely, cost the lives of many more Americans and Iraqi civilians, and create an oozing cesspool for terrorist groups to recruit and train.
In the long term, the risk in Iraq is that children who once went to school to learn to read, write and count will instead spend all of their academic time on the kind of “religious” education that helped to create a generation of terrorists. That would be, in every sense, a worst case scenario. And it’s already looking like a trend.