So as many of you know, the new suspected races are the worgen and the goblins. This has been brought about because the data miners have found two new sets of very detailed Halloween masks. Now at first I was like, well goblins make sense and a werewolf mask would make sense too. But a female worgen mask? We've never seen a female worgen ingame, and she has make-up on. Now let's get into some of the lore here, aka would it make sense.
This is extremely believable for a new race for the horde. They already favor the horde, and they're the primary cross continent travel for the horde. One of the trade princess could have got pissed at the alliance and sides solely with the horde.
Well there's two options here for what we could see. The people of Gilneas could have been changed into worgen. They use to be part of the alliance and from what I understand people can be turned into worgen. The second option is the worgen that were under the influence of Archmage Arugal are free to do whatever they want. From what I've read the worgen homeworld is in a all out war between the worgen and the Lords of the Emerald Flame. As far as I know the only emerald fire is from fel magic, so I'm thinking the Burning Legion. Also they have a previous relationship with humans and night elves so them siding with the alliance is a lot more likely than the horde.