What does this mean? Possibly nothing. It could be a hoax, it could be an unrelated property, it could be almost anything. There's certainly some possibility that it could be a new expansion to World of Warcraft, with plenty of possible meanings for what it might contain.
So is it a hoax, the next expansion, or something else altogether? That's up to the individual to guess. What we can say with certainty is that if these heroes don't get to ride on the storm, the game will have missed a golden opportunity for a pop culture reference, and that's just not likely to happen.