From what I've seen, Legion is pure fanservice. Like, whoa... fanservice.
1) Demon hunters, finally
2) PVP talents, finally
3) Ashbringer
4) Mention of the Emerald Dream
5) What appears to be the return of class quests
I had totally forgotten about the announcement today, so I missed all but the last 5 minutes of the livestream. Going to see if I can find a replay of it, because people keep commenting about only two races being able to play DH, and I don't see a mention of that in Boub's notes here.