50,000 Troops in Iraq Until 2011, 0 in 2012?

Confusing piece in the Washington Post about President's Obama troop-withdrawal announcement. The headline is that the U.S. will be "leaving 35,000 to 50,000 [troops] in place until the end of 2011," but then later in the story, we see this:

"It will be structured in such a way . . . to allow us to address some of the fundamental issues as it relates to the health" of the overstretched U.S. military force, one official said, both in relation to Afghanistan, where Obama last week pledged to send an additional 17,000 troops, and "then ultimately as it relates to using this period . . . with a very hard end date" for Iraq. That date, Jan. 1, 2012, was set as the deadline for final withdrawal of all U.S. forces, in a status of forces agreement signed last year by former President George W. Bush and the Iraqi government.

The officials said the Obama administration regarded that date as "binding," although Bush, in seeking approval of the deal from Congress, insisted that was nonbinding on a future president. The officials rejected any possibility of a permanent peacetime U.S. force in Iraq such as those in Germany, Japan or South Korea.

So, 50,000 troops on Dec. 31, 2011, zero on Jan. 1, 2012? Sounds unlikely. Theories/insight welcome in the comments.