In a press release just before the CD Projekt Spring 2010 conference, the Polish developer formally announced a sequel to their 2007 RPG The Witcher. The Witcher 2: Assassins of Kings follows shortly after the events of the first game, and concerns a string of assassination plots against human leaders; the Witcher Geralt is somehow caught in the center of things. It is not known if choices and endings from The Witcher will carry over, and a release date has not been announced.
The press release in its entirety can be read here, and the official trailer is hosted on the game’s website. Do note that the trailer contains some spoilers for those who haven’t finished the first game.