"... the Sunnis as well, and the Kurds, are inclined to think that this is going to be settled, eventually, in an outright civil war, in consequence of which they are very, very unlikely or reluctant, at present, to make major concessions."
IMHO - "reluctant"? - Maybe "not so much" if your position is eroding.
Let's see; in terms of the ability to prevail in a civil war, the Shite (w/Iranian help) currently hold the upper hand. So, the Sunni get arms (and organized military and police) if they fight AQ (as many Sunni now seem to be doing). Now the Sunni become stronger militarily and organizationally. AND, since the Sunni are working with the US to destroy AQ, while Mookie and Iran are giving the US a difficult time, the Sunni move toward the moral high ground. Do the Shite majority really want that to happen?? This situation could lead to loud shouting between Petraeus and the Iraqi (Shite) leadership! /sarc>
The Sunni are finally getting smart! This Petraeus guy is smart!