...Exp...

[Hitshade]

At this point you could argue that all but 4 classes (rogue, mage, hunter and warlock) are hybrids. All other classes are capable of performing at least 2 roles in a raid. Given a tank/dps hero class was added in wotlk I dont think it would be far fetched to say that a healing/dps class would be next. Whether or not its an Archdruid is debatable, but from a balance standpoint I would still bet that whatever comes next will be capable of healing.

They did say that the dk was only the first of several hero classes planned. I cant see a blademaster being the next introduction, given it would likely be too similar to other plate wearers.

All the signs seem to point to a Malestrom expansion... so if we want to relate Arthas with the Death Knight hero class, an arguement for Archdruid/Healer could be made as follows:

Azshara wants revenge on those who stood in her way. Namely; Malfurion, Tyrande and Illidan. Illidan is dead, Malfurion (the most powerful Archdruid) is lost in the Emerald Dream, leaving only Tyrande (a Sentinel and High-Priestess). One could surmise that Tyrande may realize the threat Azshara would pose to Azeroth and begin training other Priestesses (or even Sentinels... hmm... another hunter like class?) or find a way to commune with Malfurion and Cenarius in the emerald dream... Perhaps having Remulos train new Archdruids, or even Dryads.

All speculative of course... a lot of this lore also ties in with events surrounding the Emerald Dream, so who knows. There's also the problem of the horde to consider when it comes to Tyrande... to say nothing of the fact that it was the horde who killed Cenarius, idk.

Fun to think about though, right? lol

Edit: Dawn's on me that Sentinel/High-priest probably wouldn't fly as a new class given the Horde dont share any similar heroes. They do have druids though, and maybe the Tauren are nice enough that Cenarius and his children would forgive them for joining with the greenskins that killed him.