The epitome of niche, Swamp Wraith was originally printed as an uncommon in Future Sight. It hit $4 before Wizards decided a reprint was due, in the original Modern Masters 2013, and the reprint came at common (which is essentially real-world uncommon).
This will definitely see another reprint, could be soon, could be years. It will happen. Does see Legacy play, so could even find a home in the forthcoming Eternal Masters set(s), as well as future Modern Masters sets or even base sets. It's powerful and narrow, yet understated.
Modern Masters copies are your best bet right now (MM2013 Foils are currently half the price of the original Future Sight Foils... additional reprints of the same or of different artwork will both cause the prices to equilibrate, and the higher of the two is the more important price, still somewhat fresh from the MM2013 reprinting, rebounding, soon into new territory.
You can see the obvious difference in slope for the non-foil and the Foil copies - the foils are lagging, and this means get the foils (if we can assume a tendency for the Foil to Non-Foil price ratio to restabilize after the coming spike, which is naive but not foolish).
This makes the MM2013 Foil copies the highest yield printing overall right now.