It's nice that Span looks to be good again and Bryce has ascended directly into baseball heaven, but two bats don't make a team. Every other bat on the team was a question and "Will Jayson Werth return to form after injury?" now got an answer. No. Not this year at least.
What are the Nats' options? The easiest thing, and probably smartest thing, would be to plug Michael Taylor into
If we take a macro view we get even more set on Taylor. He's 24 not 28 (Moore) or 30 (Robinson). He has 102 PA in the majors not 502 (Moore). He was killing it in AAA (ok they all did that which should totally tell you how much that actually matters, especially for older players). He's the likely CF replacement if the Nats let Denard Span walk, which was a given at the beginning of the year (I think now they might try to float him a 2 yr deal). Giving him an every day major league job makes sense. If he totally flames out - it's ok to move him back down and try to come up with something else. But he should be the everyday starter from now until say... the All-Star break. Something like that.
Moore and Robinson, as noted, are the other options and aren't very appealing. They may hit a little better than Taylor. Moore would almost certainly give more pop. But they will likely hit for very low average with little patience and frankly can't field or run. They are questionable bench guys, forget starting. McLouth, the original OF depth, is still out from shoulder surgery. denDekker, who they traded Blevins for to get more OF depth, can't hit even in AAA. Difo is an IF who doesn't have any compelling reason to leapfrog Taylor. The minors are a mess. How bad is it? The best hitter playing OF in Syracuse is hitting .241 / .343 / .345 and is 26. The Nats literally have no OF in their system that you'd consider a prospect with Goodwin floundering and the very fringey Rafeal Bautista first struggling in High A and then getting injured.
A trade? Possible but there doesn't seem to be a need for it now, with Taylor available. You wanted him to play OF next year so dealing for what essentially is a 4 month rental is risky business unless you can get someone for a steal. I'd explore this path, you know kick the tires on some guys, but only to get a feel for a deal that you may have to make in 6 weeks, not to do anything right now.
The other side of the injury is what this means for Werth going forward and it's likely not good. He did recover in the past from a wrist injury but he was a relative pup of 32 going on 33 when that happened. He's 36 now. Even then it took a whole season of playing to regain his power (it was June 2013 when he started to hit like normal), meaning that if he comes back in August the likely scenario is that he won't have any significant pop until next year's stretch run, or more likely 2017.
What does it mean for Werth's "legacy"? Well subjectively the fans will still probably look at him positively. They like him and he did well enough in the past 3 season, when the Nats were winning, that they associated him with it. Objectively it's going to be hard to say that contract is a winner, given that it likely produced something like 2 1/2 good seasons in 7 years. Then again Werth surprised me once turning what looked like a sure bust in mid 2011 to a maybe winner by the end of 2014. Perhaps he can do it again. And even if he can't pull out a good regular season in the next couple years (spoiler alert : he can't) he could still deliver big hits in a playoff and getting the Nats into a WS or winning one, well that's worth a lot in itself. Like I said, we can't deliver judgment until it's all over and that's over 2 years from now.