Need any more evidence as to just how damn popular Pokémon Go is? How about this — we're a week out from the game graduating from beta status. And today it crossed the 10 million downloads threshold on Google Play. That puts it in the 10 million-to-50 million category. So it could be a little while before we see it jump to the next level. Or it may come sooner than we think, especially once it starts opening up to more people in more countries.
And the 10 million number doesn't mean that 10 million people are actively playing it on Android. That's the total number of downloads, and is the only number (well, the range anyway) that Google presents publicly. Only the developer knows the number of current installations.
But in any event, that's a big milestone that was reached very quickly.