In Mists of Pandaria a lot of players have gotten the Legendary back by completing the quests/ raids necessary.
Now to add, I haven't played on Mists of Pandaria in a while (With that I mean fully dedicated) so I'm not sure if that changed. All I know is, the cloak was (and perhaps still is) obtainable.
On WoD, I can't say anything since I do not play there at all.
Legion, they will most likely focus on releasing dungeons, WQ's etc. before the legendaries. But it really depends.
Head Game Master Clegane - Garrosh