I believe it is Warlords of Draenor. I also believe the supposed leaks about that same title are fakes, just like the fake leaks about MoP after the name was trademarked.
However, I would still be more than interested to see The Dark Below as the expansion. When it first came up I was sure it was the expansion. They would be trying to capitalize on the popularity of Minecraft (emphasis on exploration of a cavern 'continent', long forgotten mines, with a naga and old god twist). It sounded like a Blizzard thing to do, and I would have enjoyed it immensely.