Bryce Harper is an all-timer of a prospect. You make room for him. He still has made some big plays in big games. FP and other reports have talked about how the veterans have done their best to help him develop, and the team has been tearing it up with him playing. He offers value even when slumping. He plays in center or the corner as needed , is slowly cutting down on stupid throws, and is excellent on the bases when he gets there. When he doesn't start he gives you a good bench piece.
He has had some more days off lately. I think if the Nats keep a comfortable lead he'll play more days than not, but if the lead tightens you'll see Moore get more platoon bats. Bryce Harper simply has too much talent and ability to impact a game that you don't send him down. Even if his playing time is cut he is still someone you can use a pinch runner/hitter and put in the OF late in games.
You don't have to go 100% on building for the future or 100% playing for today. The Nationals have done a good job building a team that can contend for this season but not risk the future. There's a reason other teams are scared of the Nationals. We're nursing along future superstars in Bryce Harper and Stephen Strasburg yet we are likely going to make the playoffs and be a big threat to anyone.