As previously announced, the first DLC pack for XCOM: Enemy Unknown, Slingshot, will be coming this week on the 4th December for PC, Xbox 360 and PlayStation 3.
The DLC introduces a new set of linked Council missions, where players "will meet an enigmatic Triad operative, divert an alien ship’s course, and do battle with the aliens in the skies over China." The DLC will come with three new Council mission maps, and a new playable squad character who will come with a unique story and voice.
The price was also announced for Slingshot: it will cost 560 Microsoft Points ($6.99 USD).