Pokemon has been around for some.. 2 decades. Not everyone has seen the anime or played the older games, but hey, they're still selling lol (even without pokemon go). It's expected that a lot would quit playing it after some time. Seeing as most of them are millennials who won't even recognise a mewtwo when they see one (a friend of mine at work, took a 'which pokemon are you' test and got mewtwo so she asked me who it was and how to catch it, she's not a millennial tho, she's 30-ish).
By the time there's a new update, the rest of the world will follow again, and leave again. The thing is, in the end, it's just another game, like Tetris (which happens to be the best selling video game ever for GBA and GBC). But I don't know anyone in my circle of friends who plays it (might have, before, but not anymore).