Dan Reed at GGW has an excellent analysis of recent growth in the Washington region. In places like Alexandria, infill growth such as Potomac Yard and tear downs of oily old industrials and warehouses in Parker-Gray helps to alleviate sprawl.
Yes, Greater Washington is growing a little more slowly than it used to, and that's okay. The big news is that unlike many metropolitan areas in the United States, we're growing at the center, not at the fringe. Not only does it make our region stronger and more sustainable, but it shows that other places around the country don't have to accept unending suburban sprawl as a given.