This actually isnt entire true. When you look at the graphs it may be flatlining again, but that is due to the scale of the axis. Its baseline before NEXT was +-1500 people, its baseline after NEXT became +-4500. Sure, there was a massive spike that then died out again, but the net result is that the actual core group of players tripled. NMS before next was almost a graveyard, and it is now quite healthy.

Thats the thing with these graphs: sure it went up, that isnt surprising. What is a bit surprising is how much it went up. But it will indeed go down again. What will be interesting then will be how far. Will it dip below? That would mean people gave 3.3 a chance and just gave up on the game. Will it be higher? Than FD managed to solidify the core base, which is good news for the next DLC sales for them.