Robin talks about the Worgens storyline and for me they are a race that I'd like to see more of. I have completed the Worgen starting area, Gilneas, once and I really enjoyed it. I felt it was very story driven but once I'd completed it that was it. I haven't had a chance to complete the Silverpine Forest quests which are Horde only anyway. So I'd love to see more Gilnean / Worgen story open to both factions!
Another race that I don't really feel I know a great deal about is the Draenei. I loved the starting area and I get the whole they came from space and crash landed etc. But I want to know more about their homeworld, their way of life etc. Did they live in trees or in floating homes like I imagine them to? I guess this would be an great expansion storyline *fingers crossed*.
Perhaps as I'm not much of a reader and not a fountain of Azerothian knowledge I'm missing something! But for me, regardless on what story exists, I'd love to see more about these two races!