I have to echo other users' thoughts and say that, while this is pretty cool, that's all it is. The fact that they haven't got the full 100-strong 2nd generation is baffling to me, considering how many resources apparently go into each one. They nick the models from the main series, and each individual Pokémon has very few unique attributes besides typing and moves. The whole of Gen II should've been included months ago, and we should be getting Gen III now.
However, GO is still going stronger than I think a lot of people realise. It's not crashing app stores like it used to when it was first released, but I still see plenty of people out and about holding their phones in suspicious positions. My parents still play the games (despite having no interest in Pokémon) and many kids who get on my school bus do as well. If they included maybe 50 new Pokémon now and 50 in a few weeks time (so as to not alienate players too much) I think it would have been a really effective way to breathe new life into a game which will inevitably end up dwindling in popularity until it can't keep up its server costs.
Ideally they should be releasing 1 Pokémon every 2 or 3 days, and then posting what Pokémon is released on their Twitter or whatever after the 2-3 days are up. That'd be effective marketing, would keep up the sense of awe and wonder that Pokémon GO used to have and would make it so people aren't bored of the original 151 for so damn long. It's been half a year since its release, so new Pokémon this late is a little bit embarrassing.