Do you mean completely or to the point of getting to a point of a lot less active people? If you mean completely, i doubt ever since there's still people playing ACGC on a regular basis. If you mean a lot less active people, then ACNL can be defined as dead and buried since a lot of fans have moved on from the game either completely or they almost never play.
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New Leaf will still be played a lot until the next main Animal Crossing game comes out. Even then, there will still be people who play it. After all, there's still people who play the Gamecube game, many years later. The active number of players will just be less.
