Which one do people believe more. Dark Below still has a lot of followers, even though the trademark disappeared weeks ago, and lots of people like Boub and those from Gamebreaker and WoW Insider have stated that they don't believe The Dark Below will be the next expansion. Warlords of Draenor, just recently trademarked, is popping up just shortly before Blizzcon and has good chances of being the real thing.
No option for undecided or both or neither in the poll. Make your choice, which one do you think is more likely (not which one you would rather see).