The name, and this big change to an existing set-up, suggests that this expansion might well be more narratively-driven than any before it, and might make a big use of phasing. Perhaps we'll even see phasing of some of the neutral Goblin towns to become Horde outposts at higher levels, assuming a later point in the chronology equates with a higher level…
Oh, and the goblin models appeared to receive a retro-fit to allow full clothing use back in one of the last BC patches. Now, why would they have done that…
Their Bark is Nearly as Bad as Their Bite
It's easy to forget that there are two distinct groups of Worgen in WoW. There's the werewolf-style group who you find in Silverpine and Grizzly Hills, and who are derived from the work of Arugal, and then there are the "true" Worgen, in Ashenvale and Duskwood, who were drawn through a rift opened by the Scythe of Elune to Azeroth.
My guess is that we'll see the latter group, rather than the former. It would be cool for Blizz to introduce a race that looks completely different during the server night from the server day, but I can't quite see it happening. My instinct is that Blizz would feel that it makes this one race more attractive than all the others, and that they wouldn't go with it.
The Scythe of Elune has been almost exclusively an Alliance concept. The two major quest chains (the original one starts in Duskwood, a later one was added in Ashenvale) are Alliance quests, and Alliance questers get another big taste of its presence in the Grizzly Hills. This, coupled with the fact that users of Torment of the Worgen books in Karazan got a huge range of animations, including emotes, suggest that Blizzard has been doing the groundwork for this for a long time.
And that makes sense: eventually the fight against the Burning Legion will take us off Azeroth again. Draenor / Outland is done, and Argus feels like a big leap yet. How about another world where battle is joined with the Legion? How about the Worgen homeworld?
There's nothing saying that the playable Worgen can't be quite different from those we've seen so far. After all, if someone opened a portal to Azeroth and only the Defias came through it, that other world would get a rather skewed perspective on humans…
And, of course, Wolves are very lunar-aligned in most mythologies, and they appear to be linked to Elune in the Warcraft lore. Could in be that their appearance in the Alliance be further evidence of a Sun / Moon split between the Horde and the Alliance?
And one interesting little co-incidence – King Varian Wrynn, the new poster boy for Alliance Plot, has another name: Lo'Gosh. And what does that mean?
The Worgen would fit perfectly with the less clean-cut, more aggressive Alliance of the Varian era. In fact, they'd shake the Alliance up so much, I'm really hoping this is true.
A Random Thought
What if these races are, in fact, Hero races? They start at 65, with a narrative starting zone as strong as that for the Death Knights, that leads to the Worgen coming to Azeroth and the Goblins joining with the Horde. Indeed, I'd expect the racial starting zones to be Phased, even is they do start at level 1 – and the latest changes to mounts and the expansion of Heirloom items suggests that Blizz is even now paving the way for making the 1 to 80 run as quick as possible.