This short item by Mark Hosenball in Newsweek seems encouraging:
Analysts at the Defense Intelligence Agency have begun war-gaming scenarios for what might happen in Iraq if U.S. force levels were cut back or eliminated, say counterterrorism and defense sources. The officials, who asked not to be named because of the sensitive subject matter, declined to discuss specifics of the DIA analyses, which they indicate are in the preliminary stages.
Some officials say that people in the intelligence community are leery about engaging in speculative exercises for fear of being accused by conservatives of undermining George W. Bush’s administration policy. However, others say that this analysis could support staying the course in Iraq if a U.S. pullout would result in greater insurgent violence or a religious civil war.
Of course, figuring out what would happen if the United States pulled out of Iraq or not is only one half of what people need to know to make the relevant policy choices. The second half is whether the U.S. remaining in Iraq would help to avert “greater insurgent violence” or “a religious civil war.” (And yes, a minor civil war in Iraq does seem to be carrying on at the moment, but it could get so much worse: think Lebanon in the 1970s and 80s.) But if the worst case scenarios will happen no matter what the U.S. military does, then it’s time to beat a hasty retreat. If not, then not. Also, this sort of intelligence report seems ripe for politicizing—especially if “people in the intelligence community are leery about engaging in speculative exercises”—but it’s hard to think of a situation more in need of sober analysis at the moment.