Naturally there is always going to be a certain amount of player decline over time, but I have to wonder how much of this could have been saved had Sony not created a PR nightmare for the game with the required PSN account linking.
That said, I'm sure there's going to be a sharp spike in players very soon, as Arrowhead should be releasing a new enemy faction into the game very shortly, which is going to bring a lot of players back again for a while. Hopefully they'll find a way to keep those players interested again.