The weird part is that we haven't heard anything else about the subject for ... quite a while now, actually. Kisirani hasn't made any posts about the new combos since her comment about Sunwalkers, and we haven't seen any new quests or in-game events that acted as introductions, either. This makes me a little worried. Was this plan abandoned?
I'm trying not to be too hasty. We won't be able to play them before Cataclysm anyway, so some of the new combos may be introduced over time via the long pre-Cataclysm world event. especially those that require explanation no matter what. Case in point: I couldn't see them adding dwarf shaman without tying in the Wildhammer clan somehow (Zarhym just popped up today saying that the Alliance would be supporting the Wildhammers in one of Cataclysm's new battlegrounds, so that must mean something).
But what about the other poor slobs, the combinations that just "kind of make sense" at first glance? Are they doomed to just show up and act as if they were always there? No, Archdruid Tuj'uku, you were not always a member of the Cenarion Circle. And you, Archmage Skullmaul over there. Are you digging through my trash? I'm calling the cops.
World of Warcraft: Cataclysm will destroy Azeroth as we know it. Nothing will be the same. In WoW.com's Guide to Cataclysm you can find out everything you need to know about WoW's third expansion. From Goblins and Worgens to Mastery and Guild changes, it's all there for your cataclysmic enjoyment.