Reports are the Pentagon believes troops levels can be dramatically lowered by this time next year. This next 12 months is going to be a watershed period. If Iraq can become relatively stable and democratic and the majority of the US forces are on their way home by next summer, the war will have to be accepted as a smashing success by all reasonable observers.
The consequences of that vindication are, I think, equally frightening to the Western left and the jihadist/Baathist insurgents and terrorists. I expect the rhetoric of the left and the terrorists to continue to converge (the Iraq war as a "root cause" of terrorism, illegal invasion, puppet gov't, etc) as their desperation grows into panic at the horrifying specter of a free, democratic and independent Iraq imposed by American military force and the even more terrifying implication of a precedent set.
Of course, the bad news from Iraq will continue regardless of the actual situation because large segments of the mainstream press are ideologically wedded to leftist viewpoints on the war and committed to proving that the invasion of Iraq is a failed policy, but I think that news will become increasingly trivial and disingenuous. Already we see the beginnings of that trend: misleading comparisons of electricity availability (typically they give a number of hours per day available in Baghdad compared to pre-war, conveniently ignoring that Saddam stole electricity from other regions to keep the lights on in the capital, and that decreased availability in hours is largely due to the fact that while total electric production is now actually slightly higher than prewar (4,153 MW vs 3,958 MW) , demand is much higher due to the extremely rapid postwar economic growth), gas shortages (similar explanations exist here), and postwar civilian casualty reports that ignore the fact Sadddam murdered people at a rate just as high or higher before the war. We can expect lots of reports that the Iraqi Army, Police and National Guard are not conforming with the highest ideals of courtesy, professionalism, and decorum. Anything less than perfection will be shrilly brandished as evidence of failure, with increasing desperation as a picture of overall success emerges.