Varimathras is a nice update although he retains his old animations and emotes (you can't really see it from the perspective of the screenshot above, but I think his legs and hooves are a significant improvement on the shaky anatomy of the current dreadlord model). Both he and Alexstrasza's changes are somewhat less shocking than the complete overhaul to Wrynn and Sylvanas, but we're still pleased to see Blizzard taking an interest in the visual badassery of major faction leaders and NPC's. I would tend to agree with Zach Yonzon's contention that it would be amazing to see an update to all the faction leaders if Blizzard could swing it at some point, although I have the sneaking suspicion, judging from what CM's have said about the difficulty of programming in new Druid forms, that this is a fairly lengthy process. However, after seeing the model changes in the beta, I don't think anyone's going to argue it's not worth it, and a number of people have argued for player model changes as well. The extraordinary design work in Northrend will probably add fuel to that fire.
Gallery: New models in Wrath Beta patch 9014