According to the post at Ubisoft's Twitter, the PC version of Assassin's Creed 2 has been pushed back to Q1 of 2010.

The same post notes that developing team needs "a bit" more time in order to deliver the best quality game. As you all know, Ubisoft's Assassin's Creed is one of the games that feature the Nvidia's TWIMTBP logo, and we wouldn't be surprised if this delay has something to do with Nvidia, and that we might see this game bundled and closely supported by Nvidia.

Nvidia and Ubisoft might be working on a sweet surprise with Assassin's Creed 2, and we are sure that more info will follow as we come closer to Q1 2010.