No way, I'm still playing it constantly. This game has been the longest game that has kept me entertained, and it's still going on. I got it on Christmas, and I have been playing it massvily ever since. This is my favorite 3DS game and my favorite video game tied with Super Mario Galaxy 2
Yep, it died too fast. The PWP aspect and the bell trade and the stalk market and bug farming all contributed to the killing of this game. They all made it so that you could get everything you wanted really fast, not to mention the really high TBT/IG bell rate so that keeps people set on their ACNL needs for quite some time and that just gets boring quickly.
I also think it has to do with which site you're on.
Compared to TBT, people I meet on Gamefaqs are almost always asking for tours and to play. Which was cool for a second by the way, but they end up wandering off and examining everything I have on the ground (valuables, bells) and even trampling flowers. Anything a rude guest would do. Anywho, I guess since that TBT is far more structured, TBT users are purposely being uptight about their towns for either that reason (rude visitors), fear to meet the sort, or simpy because they just don't want to. Over time, I guess users learn what they like and dislike about online play and trade.
Well, for me New Leaf is on par longevity wise as Wild World. I'm at over 900 hours into the game, and ultimately ended up owning 4 copies of Wild World which probably netted well over 900 hours of gameplay between them, mostly because the game or DS would get lost or stolen, but I was playing WW right up until the release of NL. To be honest, even though I played a good bit of city folk, the game just didn't hold my attention for long. The game is better suited to be portable, i.e. something you can pick up here and there as opposed to sitting down, booting up your console, and playing for several hours.
I've seen a bit of a decline, of course, because of Pokemon X &Y and along with Super Smash Bros Brawl, but I think that AC is a different kind of game, it's one that you can leave for a bit, come back to, it's there for when you need it. This is because it is a simulation game. Of course, after a while you get to know things, but when you stop playing it, then later you want to get back to it, at least that's what happens to me.
When I got Tomadochi Life I played that consantly, but it does not compare to the hours I've played Animal Crossing. I've still seen some people still play and that makes me happy. It keeps the game alive.