Gamers seem to tie "popularity" to "life" when it comes to games. They couldn't be more wrong if they tried.
I never take any consideration to whether other people plays a game or not when choosing what I want to play. I keep going back to some games which have at most a thousand players still playing them often - this may be due to being raised back when multiplayer was "invite three dudes home and fight over who gets the least broken down controller" and due to this, playing against/with complete strangers never grew into me.
Sure, some games need a fanbase (MMOs) but I think Terraria is one of those games that will still be played by gamers ten years from now - that is what makes a classic, not how many hype-riders buy the game five months before it's released.
Content can extend a game's popularity, but its "life" is an objective thing. Did you know Doom, a game from the early nineties, still has maps and entire campaigns being created even today? Did you know Diablo II is sure to outlive its sequel, as much as Dungeon Siege 1 survived its two sequels?
Did you know there's people out there still playing games for computers and consoles from the eighties? I regularly ragequit from a few ZX-Spectrum games, myself, and one of my top five games is from the old NES.
So to answer your question, do you think it's dead? That's all that matters. I would guess you don't think it is, since you're still in the game's forums.