I'm sorry but those thinking this is going to fade are crazy. Kids, when they get excited, do things over and over again. I remember when I was a kid, I could watch the same movie everyday for like a week if I liked it (and enjoy it like I was watching it for the first time). When you're a kid, you don't get bored of things nearly enough. I have seen so many kids, teenagers, and adults in 20's/30's on this game and I have two thoughts on why it won't fade:
1) The kids won't get bored. Everywhere I go I hear kids talking/referencing pokemon now. This is basically becoming the next minecraft to them, which is funny because minecraft was this past generation's pokemon (at least in terms of what it meant to their and us 90's kid's childhood). It isn't going away in their minds.
2) The older demographic, the one that grew up with pokemon, loves this return to their childhood. But more importantly, this group (of which I am part of) is also fitness obsessed (or at least increasingly becoming so). If we weren't, things like Fitbits would have died upon landing, but they did just the opposite. I am a teacher, and myself including a ridiculous amount of other staff members at my school have fitbits and are obsessed with competing with one another and burning calories and getting healthy. Pokemon Go only enhances that experience, and people ARE treating it like a fitness app (I love how it has the badges for distance walked).
Miitomo sucked, had no fitness application, and didn't even have game elements to it (unless you consider answering questions a game, which I don't). I stand by my prediction I made in a previous thread:
In 5 years after release, this game will have acquired 100 million downloads globally.