So we are back to the 10+ year commitment. It's not that I disagree with all your scenarios which all seem possible, it's just that we have a choice: commit to a decade or longer or pull out. The middle ground does not work. And you know as well as I that we don't have the military personal or the political will to sustain what we need to to make this work. Since we don't, it is pointless to pretend otherwise. No?
I do not see how the middle ground doesn't work. The facts on the ground have changed substantially. Security in Anbar is much better and no longer probably depends as greatly on an American troop presence.
With that said, having a significant number of American troops with "boots on the ground," ready to go kick ass of any militia that thinks they can swoop in on some city and kill all the men there would be a real deterrent against the worst excesses that might happen if the only military assets we had in the region were aircraft carriers, bombers and surface-to-surface and air-to-surface missiles.
I agree about the fact that folks in the miltary have really gotten the shaft since the war began. I also agree that it is time for them to go back to the amounts of active duty they were accustomed to before the war began. I just think that it's probably possible to do that and still maintain some bases in Iraq, which I think might do a lot to keep the worst excesses at bay.
It might take 10 years, but it's not 10 years at the current rate where the military is stretching so much it's about to burst at the seams. The point being, you said in your post that we couldn't secure the country with 100,000 troops for 4 years, why would less than that work in the future? Well, a lot of things are different now. It is simplistic to simply say "well in 2006 100,000 troops on the ground meant X number of murders and now in 2007 130,000 troops on the ground means .5 * X murders. Therefore it is that extra 30,000 troops which made the difference." This is giving Bush a lot of credit; who knew that 30,000 extra soldiers would halve the violence in the country? Why didn't we just do that in 2004?
Sarcasm aside, the fact is that a lot has changed since 2004, or even 2006. The Sunnis now seem much less welling to harbor Al Queada, and even if a national reconciliation where all political disputes are settled is not just around the bend, I can imagine how the changing dynamics of power in Iraq might mean that a long-term commitment of 30,000 soldiers in Kirkuk and Erbil might
(might, might, might) be effective in keeping a lid on the country, keeping it from disintegrating, and allowing the U.S. to lick its wounds and allow the military some breathing room.
Again, this all or none strategy you seem to have seems a bit fatalistic. Either we're there at current troop levels for another 10 years, or we get out completely. Why? The security situation in Iraq is a complex mix of things, only a couple of factors of which we control-- those being the number, location and mission of American troops. The rest of the picture comes from the relative influence and power of terrorist groups and extremest militias versus less radical groups, the demographics of the country as regions that were once heterogeneous now become homogenuous, the will of the average Iraqi to continue in armed struggle, the ability of Al Queada to smuggle in suicide bombers, the disposition of Iran to either ramp up or ramp down the chaos. I could go on and on. And the surge only adjusted those factors which we control, it might just be a coincidence that it happened to coincide with an exogenous drop in violence. Or who knows (I'm sure you'll like this one) perhaps the fact that the U.S. seemed to be rededicating itself and not on the verge of pulling out gave, say, the Sunnis who threw out Al Queada the confidence to do so without fearing grave repercussions.
At any rate, with the situation so dynamic and being so complex, I don't see how you can look at the range of possible outcomes and say that only two are viable: the U.S. stays, at near current troop levels for 10 years or else violence spikes back to its old levels, or we just get out completely. (What exactly do you see as the consequences of a complete pullout, by the way? Does it matter if they are horrible?) I think there are almost certainly multiple paths down the middle between those two, and I bet that the next President likely navigates one. I wish him or her the best of luck in navigating it successfully, because this is one hell of a clusterfuck.