Of course, this isn't too surprising, really. As it turns out, sources close to the TCG say that all development and art for the game has been done inside Blizzard for a year or more -- Upper Deck has only been providing the printing. They've either been preparing for the switch for quite a while, or ... well, I can't really think of any other reasons. Why go elsewhere when you could get it done internally anyway?"As some of you may already be aware, we will not be renewing the World of Warcraft: The Trading Card Game license with Upper Deck. We want to assure you that we are committed to supporting the TCG, and players can look forward to new content and strong organized play support in the near future. We will share additional details about the game's transition to a new partner as soon as possible. For those awaiting tournament prizes, we will ensure you receive them."
Licenses are big money, and contracts require that they be active for a certain amount of time. Companies can always choose not to renew their licensing agreement if they feel things aren't going well, or for any reason, really. But this is Blizzard, and this is a business move, pure and simple; you needn't worry that the game is going anywhere. It just might take a little bit to get everything back on track.