The deadlines seem to be clear: in July of 2011, the transition to the Afghan army begins in earnest, and U.S. troops are supposed to begin their re-basing. A drawdown has always been conditional, and conditions, to put it mildly, don't seem that ripe a year out. In congressional testimony, Defense Secretary Robert Gates made it clear that the drawdown would be multi-phased, in that certain regions would see the transition before others. Nonetheless, President Obama all but promised that the date is set in stone; U.S. troops are going to be coming home, even though Gates himself negotiated the wiggle room for his commanders: subject to conditions on the ground, the slope of the curve would be variable.
The Pentagon, meanwhile, is preparing for a much longer stay.
Check out this solicitation for a fuel contract. The Defense Logistics Agency needs to supply Bagram Air Base with enough fuel -- hundreds of millions of gallons worth -- to last from September, 2011 through August 31, 2013. That is, the contract begins AFTER the drawdown is supposed to begin, and lasts for two years.