tom Davis also comes from a house district which is trending strongly Democratic and if he ran the house seat is likely gone for the GOP.
Uh, I think you're firmly situated in a magical fantasy land where the trees are covered in gumdrops and kittens have wings and crap gold bars.
Davis' district, VA-11, is still an R+3 district. It'd be a competitive race, but if you think its somehow a safe Democratic pick-up, well...just wash your hands after touching all those "gold bars."
That was in 2004 that it was R+3, I believe. I was amazed when I looked up data on the unflux of people moving into NOVA. Somewhere around 90,000 a year.
His district may be growing, but it's not going to go from R+3 to D+10 overnight.
You must not be that familiar with Northern Virginia. As someone who has lived there off and on for the past 2 years, it can absolutely change nearly that much, considering some of the towns in Northern Virginia are growing by as much as 10% a year and many of the areas growing around 3-8% a year (almost all the growth are democrat-friendly voters from Washington and Maryland who want more affordable living).