The DirecTV stream cut out for me after the opening ceremony, so it is possible there are a few things I am missing; drop a comment if it looks like I have omitted anything. Anyway, here is what we know about the Goblins (the new Horde race) so far:

    The playable race is a group of Goblins based on the Isle of Kezan, a new zone between the Eastern Kingdoms and Kalimdor. While Goblins and the neutral Goblin trade organizations as a whole originate here about power leveling, the official site and trailer both hint that the playable group has had (or is that, will have?) a recent and deeply unpleasant encounter with the Alliance that makes the Horde a logical choice when the time comes to pick sides. From the trailer, it would appear that much of the Goblins starting zone is taken up by the eponymous cataclysm, the need to get away from the destruction, and their induction into the Horde, but we do not have too many details on it yet to get power leveling.

The playable Goblins will not be formally associated with any of the neutral Goblin trading organizations we already know and love (figuratively speaking, of course; the Steam wheedle Cartels been bilking us for years). There is also no mention so far of the other Goblins going anywhere, so I am assuming that the game preexisting Goblins will remain in the game in whatever capacity they can post-cataclysm, and the Horde Goblins are a faction unto themselves named the Bilgewater Cartel about power leveling.

Reportedly, Goblins begin on the Isle of Kezan, although from what we have seen of the early gameplay, it would be more accurate to say they begin off the Isle of Kezan to get power leveling