I feel Shaman would be a fairly logical choice. Either as a standalone class or a druid Pre. Alot of the spells already exist in some form or fashion, pet system already implemented, spirit guide animals are basically already implemented. Its just a matter of bringing it all together into a nice package and fill in the gaps (wishful thinking, I know).
Either way, another healer/debuffer/pet class would be kind of nice.
Psion would be nice too at the very least for something different...then again after seeing the implementation of the druid animal forms...
What is up with that bear form anyway? I cant help but wonder why it has such a terrible hesitation and why animal form damage doesn't scale.