Its a free game, its on an old engine, most people have followed the gaming edge to pastures new.
What you're increasingly left with are the hardcore who actually LIKE the game, people who are poor at any other game and thus stay with NS to retain some semblance of glory, and random nubs who decide to try the game.
I don't think its even close to a revival, just an influx of new blood. Same thing happened with.......errrrrr... Alliegance, when it went open. Hard core crowd still playing, random nubs, some people who play it only because they've some popularity.