This weekend, Pokemon GO players the world over are congregating in Chicago for the special Pokemon GO Fest live event. This event will be marked by the long-awaited introduction of legendary Pokemon, and if a recent trailer released by Niantic is any indication, Mewtwo may be part of the first batch of legendary Pokemon added to the game.

The legendary Pokemon trailer released by Niantic mainly focuses on the legendary birds, but eagle-eyed Pokemon GO enthusiasts will have noticed a brief glimpse of Mewtwo near the end of trailer. This is a possible indication that Mewtwo will start appearing in legendary raids along with the other Pokemon seen in the trailer, though it could also be a tease of what's to come in the future.

After all, Mewtwo was seen in one of the very first Pokemon GO trailers, shown battling Pikachu at Times Square in New York City. The game has been out for over a year, and Mewtwo still has yet to be added. Since Mewtwo was barely seen in this latest trailer, Niantic could be setting the stage for it to be added in a later event instead of on July 22nd.

Even if Mewtwo isn't added to Pokemon GO this weekend, fans can at least expect to start catching the legendary birds from both the first and second generation of Pokemon. Articuno, Moltres, Zapdos, Lugia, and Ho-oh are all shown prominently in the trailer, whereas Mewtwo is seen only briefly, and other legendary Pokemon are missing in action entirely.

Besides Mewtwo, fans may notice the absence of Mew, as well as the legendary beasts Entei, Raikou, and Suicune. Since none of these Pokemon are seen in the trailer, it's a safe bet that Niantic is saving them for a later date.

While some may be disappointed that Pokemon GO doesn't seem to be adding all the legendary Pokemon it could at this point, the five confirmed for the game should be a good start. It will be interesting to see just how difficult catching these legendary Pokemon will be once they're added to Pokemon GO during Pokemon GO Fest on July 22nd.

Pokemon GO is available now for iOS and Android mobile devices.