It seems that nothing is kept under wraps as long as it is supposed to be. Blizzard was set to reveal the next Hearthstone expansion during this weekend's tournament action. However, a photo of an advertisement being painted on the side of a building in New York City has revealed the name: Whispers of the Old Gods.
Though we'll doubtless hear more specific information about Whispers this weekend, at least we know the name and the speculation can go crazy.
Source: Eurogamer
