Like many have said here, a decline is bound to happen. Nothing stays that big forever. What Niantic wants now is a nice baseline of users who frequently use the app and pay into the system.

Quite a few people saying it's not a very good game at its core. I have no clue about it first hand. But that's some of the criticism I've read/heard.

All games decline after a time, though not usually this quickly. I'm guessing to much exercise involved

It was not as hot today and its Sunday so I did see some more people playing Pokemon Go while walking with my kids through town to the park, passing a few gyms and a bunch of pokestops. It's in the tens though, no big groups or anything.

My kids haven't asked to play it anymore for over a week. We were playing it for a bit on the pc, but without actually walking around all that's left after the initial fun factor is a repetitive grind to nowhere. I updated the PC version yet haven't touched it anymore either. It was fun to check out the sights on the map and now it's easy to spot the pokemon players as I recognize the stops and gyms, I have no clue what the lasting appeal of this game could be.

It's OK for a small decline to happen for a while. Nothing out of the ordinary if you ask me!

It's certainly in decline here, though lots of people still play it.
Casuals are pretty fleeting.

I mean, it's only natural the number of people using the app declines. I'm more interested in seeing it's baseline.

Everywhere I go people are playing. I haven't seen a decline. People sit out until 11 pm, pokelures in use with groups of strangers playing and talking. Gyms change color all day long.