According to an article from ARLnow.com, the bike lanes are in the preliminary planning stage. If and when the bike lanes are approved, they won’t be ready for a few years. At the earliest, it sounds like we’re looking at 2 or 3 years. The article includes a couple maps of the proposed additions.
Arlingtonrider – the section of Army Navy Drive to the west (taking a right from Joyce St.) has been re-striped with lanes already (I can’t recall exactly where they end – somewhere past the ANCC iirc). For the section west from Joyce – yeah, I think that’s going to take a while.