Yunel is possibly next year's leadoff man, unless Michael Taylor turns 1/3 of his strikeouts into walks or improves his BA. As for his glove, Michael probably has better legs under him but he I hope he's studying under Span's tutelage when it comes to glovework and routes taken. We are likely to be a worse club one way or another next year, with Jordan Zimmerman and Doug Fister possibly both being replaced (Roark and Cole, Taylor Jordan, maybe Treinen if he can finally iron out a third pitch), and the Trea Turner era being probably a good year away, early 2017ish. On a related side note, the way Werth is performing right now, it's possible he has officially entered the "albatross years".
We will probably still be a championship caliber club next year, Rizzo makes a couple moves to even things out a bit, but instead we'll face genuine competition from the Mets/Marlins (if they make moves) and we'll be "championship caliber" like the Mariners are supposed to be this year, not the 2013-15 Nats have been. If October goes well none of this really matters.
2018 Nats lineup:
Turner
Difo
Rendon
Harper
Zim
Taylor
Ramos (assume he's resigned, Rizzo seems to love him)
Mystery LF (trade/FA)
That's pretty damn good looking to me. Rotation could be Scherzer/Giolito/Roark/Cole/Jordan without a single addition and it'd be damn good. Bullpen featuring whoever doesn't make it (Reynaldo Lopez, Erick Fedde) and the 2018 Nats look like big time contenders once again. It's just gonna be 2016-17 that is a tad murky (a Yuni-Espi infield, Taylor still adjusting to CF, increasingly unproductive unbenchable $20m Werth).