No one knows when home values will begin to increase; run quickly from anyone who claims to.
However, I do know that area well. I lived in a townhouse in West Falls Church (across from the Giant and near the VFW Hall, if you know that area) and in a house in 22046, walking distance to the West Falls Church Metro.
So, let me give you my takes on the macro, intermediate, and micro analysis regarding your question.
Macro: Big picture: Again, no crystal ball, but I don't expect things to "get better" for a couple of years. The economy looks like it's going into a recession; there are still billions of dollars with of ARMS getting ready to reset; some other major lenders are going to go under (as Danilo suggests in his blog), unemployment nationwide is up, buyer confidence is weak, a lot of the nation's resources are being used in the wars in Iraq and Afghanistan (not commenting on whether we should be there; just that we are, and it costs a lot of money which, if it weren't spent there, might be used for more economically productive things), energy costs are high...and on and on. So, big picture: declining or flat market for several more years.
Intermediate view: The Washington, D.C., area: Quite strong. BRAC is shifting military around, but is an overall plus, some as close as Springfield--a 10 minute drive on the Beltway from Falls Church. The presidential elections generally help the real estate market in the DC area, even without a change in Administration. But this time, even if the Republicans remain in power, there will be a lot of turnover...even more if the Democrats win, as it looks like they may. Plus, major employers in the DC area include the federal government, which provides a very stable employment base, and trade/professional associations, which also are quite stable. So, generally, the DC area is more resistant to downtrends than some other areas of the country.
Micro view: Falls Church/Vienna. It's a great area: Good for commuting into DC...or to the Tysons area...or even out to Reston. It's got good transportation: Metro runs along 66 through West Falls Church, Merrifield, to Vienna. Then there's 66 itself, plus the Beltway. True, they get jammed at times, but it's a heck of a lot better than Gainesville! Fairfax County has very good schools. (Whoops! As a Realtor, I don't know if I can say that. Let's try: A number of independent studies have ranked Fairfax County schools near the top.) Meanwhile, the entire Tysons Corner area is being redone and expanded. Lots of office buildings, mixed use buildings, and entertainment. Metro is going to extend the line from West Falls Church to Tyson's and beyond to Reston. UVA and Virginia Tech have a satellite school near the West Falls Church Metro. A little bit farther out, in Fairfax, George Mason is becoming a very serious university, and is expanding greatly.
So, what's that all mean? While it's totally up to you, if you're reasonably confident you'll be around for 6-7 years, and buy carefully (the right property at the right price), I'd strongly suggest you consider buying. Even 4-6 years, possibly. On the other hand, it'd be dicey under 4 years.
Hope that helps.