According to the announcement, “Professor Willow has discovered Togepi and Pichu hatching from Eggs! Starting later today, Trainers will have the opportunity to hatch these and several other Pokémon that were originally discovered in the Johto Region in Pokémon Gold and Pokémon Silver video games.”
Unfortunately it seems that for now that this isn’t the 100 Pokemon update that we’ve been waiting for. Instead it seems like Niantic has chosen to add more Pokemon bit by bit over the course of the next few months, so for now trainers will only have Togepi and Pichu to catch, and from the 12th to the 29th of December, a special edition Pikachu wearing a Christmas hat will also be available.
Based on the comments, it seems that quite a few players are upset at this supposed “huge” announcement, but we guess it makes sense. By steadily releasing new Pokemon, it helps to ensure that gamers are interested in the game, versus releasing all at once and seeing the hype die down a month or two later.