It had a huge launch, and I kind of doubt it can get much bigger. Thus, decline is a logical conclusion to draw from that. And of course decline doesn't mean it's going to disappear: For a product of Pokémon GO's size, it'll still have a huge amount of users even if it declines a lot.
Talking about decline, I'd like to see what winter does to the numbers, and whether it recovers when spring comes. Mobile gaming doesn't sound very convenient when it's very cold outside.







