We’ve seen existing classes get applied to new races when they allowed Draenei Shamans and Blood Elf Paladins in The Burning Crusade expansion and we’ve also seen existing races get a new class with Death Knights for Wrath of the Lich King. We’ve all had to wait until the expansion came out to access them so it really isn’t a shock that the new race/class combinations announced before won’t be available before the Cataclysm expansion comes out, according to the Developer Chat on Twitter the other day.
Of course you can argue that in those previous examples there was a new race or a new class involved while save for the Goblins and the Worgen, these are existing races and existing classes. So yes, if Blizzard wanted to, they could allow us access to the new race/class combinations like Troll Druid or Dwarf Shaman right now because there’s no new race or class involved.
I think the most important thing about waiting for the expansion to allow access to these new combinations is setting up the right structure to make them feel like they not only belong but that the experience would be great. When trying to make sense of the new combinations and how they fit with the lore, there’s talk about Dwarf Shamans making sense because of the Wildhammer Tribe and Troll Druids making sense because of the Horde friendly Shatterspear Tribe and speculation that their proximity to Moonglade allowed them to learn how to be Druids. I remember when Cataclysm was announced there was a theme that the new race/class combos are a result of seeking other ways to defeat the new threat. So there really isn’t much point to seeking the help of these allies and resorting to alternative methods (like Tauren wielding the Light aka Tauren paladins) before the Cataclysm happens.
In the Developer Chat in Twitter, they also made mention of making some changes to the starting zones. We already heard about what’s going to happen to the Trolls and the Gnomes in the next minor patch and that’s just a prelude to what’s happening in the expansion. It’s a better idea to hold off on the new combinations so that players could get the most out of these new changes to the starter zones rather than allowing them now and having less players appreciate the changes in the expansion.