New Class

I know this is a bit premature considering that LK just came out a few months ago... but I can't help wondering.

Apparently, with every new expansion (supposed to occur once per year or so) Blizz is going to incorporate a new hero class into the game. I think death knights have been a hit thus far. They are a great concept and seem to be very easy to use. I haven't leveled mine yet. I'm not sure I'm going to as I'm not very interested in another melee toon AND I don't like tanking very much. Otherwise, I love the buffs they bring, I love the disease based nature of their spells, and I love the little sublteties like the creepy laugh.

With that said, what will the new class be? I'm sure they already have a list of ideas. I'm thinking it has to be a caster type unit. Another healer would be cool, but is another hybrid class really valuable? Archdruid has been mentioned a lot in various forums/posts. I just can't see this happening. Lets go over a list of requirements:
1. The class has to be accessible by a number of races.
2. The class has to be represented in WC lore.
3. The class has to be unique.
4. The class has to be associated to the new content.

Here are some other earlier ideas that we probably won't see either... Brewmaster, Necromancer, and Runemaster. I suppose we could list the Bard in there too :). In the past Blizzard had attempted to combine spell casting and melee into one class/spec ie. shamans and druids with little success. I think these classes have been improved upon but in a direction away from what was originally intended.

Any ideas on what to expect?