This is purely speculative, but I have confirmed up to 230 Pokémon in the upcoming Legends: Z-A!
About 126 of them have been shown in previous trailers and the Extended Look video, the rest are the ones from the Kalosian Dex, and the ones from lines with Mega Evolutions.
I can't believe it. There's an actual demo release date! After all these months! Maybe NOW I can bug through catching Bug-Type Pokémon and battling WITH bugs!
Hopefully there aren't any, you know, coding bugs..