The Templar Orders world-ending plan concludes on December 21, 2012
The Templar Order plans to launch their Apple of Eden into space via satellite to control the minds of the worlds population. Originally, Abstergo was going to launch the Eye-Abstergo satellite earlier in 2012, but an incident at Denver International Airport caused them to lose the Piece of Eden they originally intended to use, and thus delayed the launch until December 21. Daniel Cross was on site at Denver, and there is believed to have been an altercation between the Templars and the Assassins. However, since the Assassins never reported back and Cross refuses to discuss those events, the entire episode remains a mystery.
Fortunately, the delay allowed Desmond to recover an Apple of Eden for the Assassins, and learn more about the impending disaster from the First Civilization ghosts/holograms who continue to contact him throughout the series. With a clear plan of how to prevent the catastrophe, Desmond has returned to the U.S. to put an end to the Templar threat.
but Desmond has spoken with members of the First Civilization, and knows how to stop the Templar plan
At various key moments in the Assassins Creed series, members of the First Civilization have reached out to Desmond to pass helpful information along. One of Desmonds earliest conversations was when Minerva contacted him through Ezios memories in the past (he talked to Ezio but spoke to Desmond, it was weird). Minerva warned Desmond of the approaching apocalypse event, though details on how to stop it were sparse. As Desmond dove deeper into Ezios memories, more contact with the First Civilization was made, and more was learned about how the First Civilization fell.
With a clear understanding of what happened those tens of thousands of years ago, Desmond and his close-knit band of Assassins are headed to the location where the First Civilizations Grand Temple was located and buried by thousands of years of planetary evolution. What Desmond will find there is anyones guess, but rest assured, he will be ready to face whatever challenges wait to save all of humanity.
Everything is permitted
Assassins Creed III is due out very shortly, and Ubisoft has promised plenty of answers and an ultimate conclusion to Desmonds story. There are plenty of narrative threads to pick up and finish, including the possible truth behind the Denver incident, whether or not Daniel Cross and Desmond will cross paths, and why Desmond was the chosen one. Its an exciting time to be an Assassins Creed fan to be sure, and we can only hope this final game in the trilogy delivers upon expectations.