Dunno.
When the US "pulls out", assuming things are little changed from the current conditions, I expect the Green Zone will either become an even more fortified bunker, or that it will be over-run quite frequently by shelling and car bombings. Without the appearance of a government there, it's hard to see things doing anything but spiraling faster down the toilet. Locking down Baghdad can stop the car bombs, but it can't be done for long or the city will quit functioning.
I don't see a simple solution. If we (the US and International Community) sent in 400,000 more troops, then presumably Baghdad could be pacified. But for how long? How would it help solve the problem of developing a capable military and police force that isn't tied to the militias? Until the ties to the militias are addressed, it seems hopeless.
I do think that violence will get worse once we leave. The Iraqis depend on us for logistics and they don't have an air force. Without those things, it's hard to see how they can keep the country together when so many want to kill the others.
I fear that no matter what we do, things will get much worse in Iraq. I wonder whether there will be pieces worth putting back together by the time it's done. It's unfortunate that it's so much easier to destroy things than to build them in the first place.
:-(
Cheers,
Scott.