That information is to take with caution, Terran Gregory, the In-game Cinematic Project Director for World of Warcraft said (after a little of torture) that for the moment 6 in-game cinematic would prepare for the release of Warlords of Draenor.

Remember than for the launch of Mists of Pandaria, 3 of them were there : The Battle of the Serpent’s Shrine, and the Horde & Alliance ones.

P.S : Of course, that number could change before the final release of Warlords of Draenor.

The Battle of the Serpent’s Shrine