Last week marked the second anniversary of the release of Pokemon Go and to celebrate, Niantic will once again be hosting Pokemon Go Fest in Chicago, Illinois this coming weekend.Recently, the Pokemon Go Twitter account released a new image (see above) that features trainers and dozens of Pokemon that are already found within the game. However, mixed in amongst many of these Pokemon were three that haven't yet been added to Pokemon Go -- Chimchar, Piplup, and Turtwig. For those that might not be aware, these three are the start Pokemon from the fourth generation games -- Diamond, Pearl, and Platinum -- and their inclusion in the image is surely no accident.The advent of fourth generation Pokemon making their way to Pokemon Go isn't surprising by any means and seemed like only a matter of time. The question now though is just when Niantic is planning to start including these fourth gen creatures into the game. Even though Pokemon Go Fest this weekend will include many exclusive Pokemon available for capture such as Celebi, Niantic hasn't currently made any official announcements on whether or not fourth gen Pokemon will start to populate in Chicago. Then again, they could be waiting until the festival kicks off to make such an announcement.We'll have to see what happens this weekend during Pokemon Go Fest to learn if we will be receiving further details on this next generation of Pokemon making their way into the game.