Matt Carofano, art director of Skyrim has confirmed that there will be no werewolves in The Elder Scrolls V: Skyrim, however it might come as a DLC in this Dutch interview Here.

"Is there an idea to add werewolves into the game as dlc?

Maybe so, yes. We currently have no werewolves in the game, but it's definitely something to think about. What we do have in the game, are vampires. How progressive you will play the vampire, the more people will begin to attack you in cities. Also, the vampire is much weaker during the daylight."