https://techcrunch.com/2018/10/16/pokemon-go-update-bringing-mon-from-the-sinnoh-region-is-live/

If you’ve been laying off the Pokémon Go for a while due to a lack of new monsters, prepare to be glued to your phone again. Niantic is now adding pokémon from the rugged Sinnoh region that first appeared in 2007’s Diamond, Pearl, and Platinum games.

Of course, it’s not so simple as a dump of a hundred new ‘mon into your area. The new guys are arriving in waves, likely meaning the most common sorts will start appearing today, while cooler ones and sets of themed critters will arrive over the coming weeks.