Now this isn't to say that Pokemon Go is about to disappear off the face of the earth, but there has been a drop in the user base since its release. Many could point at the shiny new luster has started to fad, some might even point at the tracking issues, and the shutting down of third-party sites that actually made the game more enjoyable.
The thing is that the developers are still planning to continue on with their now currently 30 Million plus users, and hope that further patching will keep those left happy. I do find it slightly humorous that even though they did shed around 12 million users people are freaking out saying that this game is doomed. Personally, there's not enough data to suggest that it is doomed. If you look at any game with online capabilities, there's a spike that the beginning as everyone needs that shiny new thing, and then as time goes on those who actually find their groove in the game will stay and the rest will be distracted by the next very shiny new thing. That's just how the world turns.