I know they are working on building a dog park towards Potomac Yards, but given the uptick in apartment buildings in Crystal City, it could really use a dog park. It doesn't have to be enormous, but a big enough space to play fetch, run around, and doggie socialization would be great.
Millennials in Arlington
Washington Boulevard (especially north of route 50) would be an ideal corridor for a dedicated bike lane.
Also, what happened to the plan to extend the bike path beside Washington boulevard south of rt. 50? I thought that they were going to connect Columbia Pike to Crystal City and the Pentagon City Mall? I heard a lot about it three years ago but it has felt like deafening silence since then...