'Eye of Azshara' trademark by Blizzard signals possible expansion for Hearthstone

Related Games:
World of Warcraft, World of WarCraft: Cataclysm, World of Warcraft: Mists of Pandaria, World of Warcraft: the Burning Crusade, World of Warcraft: Warlords of Draenor , World of WarCraft: Wrath of the Lich King, HearthStone: Heroes of Warcraft