http://www.pcgamer.com/blizzard-announces-hearthstone-kobolds-catacombs-release-date/

After weeks of teasing and individual card reveals, Blizzard has announced that the Hearthstone expansion Kobolds & Catacombs will be out on December 12. Players will be given three Kobolds & Catacombs card packs and a random Legendary Weapon card for logging in after it's live, and will also have access to three one-time Dungeon Runs, each with its own card pack reward.

Pre-purchasing 50 packs for 50 bucks will also get the For the Hoard! card back, which will be handed over as soon as the transaction is completed—you'll have to wait for Kobolds & Catacombs to go live before you bust open the cards, though.