As previously reported, the latest push from the notoriously progressive Patch 2.4 revealed that a Black War Elekk has been added to the game, but some more digging has also unveiled the Swift Warstrider, a PvP version of the oversized chickens that Blood Elves ride. The models for both mounts have been in the game files since The Burning Crusade was launched but were never introduced into the game, despite slavering anticipation from many players. It looks like there'll be a use for those extra Marks of Honor, after all, as the mounts are finally available on the PTR from each faction's respective Mount vendors -- Raider Bork in the Hall of Legends for the Horde and Lieutenant Karter in the Champion's Hall for the Alliance -- for 30 Marks of Honor from Alterac Valley, Arathi Basin, and Warsong Gulch.
Strangely enough, the current model for the actual Warstrider on the PTR seems to be the Swift White Hawkstrider which drops of Kael'thas in the Magister's Terrace, rather than the customary black mount in the game files. This can possibly change when Patch 2.4 finally goes live, or it could stay the way it is... Patch 2.3 on the PTR had one color for the Cenarion War Hippogryph while there were several models found in the game files, including a lilac one that my wife fell in love with and was prepared to pony up 2,000 gold for. The Black War Elekk also currently shows the Hawkstrider icon, rather than the normal Elekk icon. It looks like the patch isn't quite ready to go live just yet. Enjoy the mounts!