Despite some commanders saying more U.S. troops are needed in Afghanistan, President Obama could very well keep the numbers much lower than they'd prefer, per the L.A. Times:
The Obama administration plans on keeping 6,000 to 9,000 U.S. troops in Afghanistanafter 2014, fewer than previously reported, and will confine most of them to fortified garrisons near the capital, leaving Afghan troops largely without American advisors in the field to fight a still-powerful insurgency, U.S. officials said.
Although it is not final, contours of the plan have become increasingly clear in the weeks since President Obama's reelection. Officials close to the discussions say the final U.S. presence will be substantially smaller than the 15,000 troops senior commanders have sought to keep after most of the 68,000 remaining American troops leave in the next two years. [...]
Bagram will become the hub for U.S. special operations teams charged with tracking and killing members of Al Qaeda and other terrorist groups, the chief American military mission after the drawdown. Bagram also will be the main air base for U.S. drones and other combat aircraft in Afghanistan, the officials said.
Zero troops would be a good number, too. In fact, it seems President Obama agrees, but unfortunately, that's just wishful thinking:
"One of the things that Obama and Karzai have always agreed on is the need for a reduced force presence," a U.S. official said. "I could see them both wanting zero, but at the end of the day I don't think that will happen."