The 2012 American Community Survey results are out and bike commuting is up to 4.1% which is almost a full percentage point above last year's 3.2%. (In 2010 it was 3.1%). And it represents a pretty rapid climb from previous years.
But DC isn't alone, the whole area has seen increases in bike commuting year-over-year.
Arlington was up to 1.8% from last year's 1.2% down to 1.2% from 1.3%
Alexandria at 1.3% from last year's 0.8%
Silver Spring was up to 0.6 % from last year's 0.2%
Here's more from LAB
According to the ACS, in 2012 about .64% of commutes are made by bicycle, which represents an almost 10% increase from 2011. This is the largest year-on-year increase since 2007-2008, showing that people are choosing to use their bicycles for transportation not just in response to economic crisis, but because bicycles are leading the way to recovery. In total, there were 864,883 bike commuters in 2012.
Update: I don't know how, but I read the tables wrong for Arlington. I apologize