Best-case would be that Rendon recovers from his injuries (which I expect) and successfully transitions to 2B. Espinosa is a natural SS and a Zimm-Espinosa-Rendon-<whoever> infield would be sick. Tons of power and OBP and some great defense.
There does, unfortunately, seem to be something of a consensus that Rendon is unlikely to be able to play 2B. Obviously, that could change, and the consensus has been wrong before, but I think in that case we're probably looking at either 1B or LF. I'd personally prefer LF, simply because it would be a shame to waste someone with his glove at the least important position defensively. Then again, from what I hear his arm isn't the strongest, so I don't know if an OF position would work best for him.
Worst-case (unless his injury is really serious), he turns into a Wright-esque 3B but is blocked by Zimm, and we can trade him for a real impact player--he'd be by far the best trade chip the Nats ever had. No way for me to look at this draft as anything but a success so far.