This is interesting, from MMO-Champ's panel recap:
The final boss of this expansion won't just be an Orc.
I've been wondering where they could go with bosses and things. I mean, for one, the Orcs haven't drank the blood of Mannoroth, but the Legion is still going to be around trying to get influence. Gul'dan is still going to be there. So we may have Legion enemies.
Interesting thought, though: What Burning Legion characters who died in history could now be returned to the story via the alternate timeline?
Will Gruul be alive on this Draenor? (Suppose it would be hard to explain why he was level 100+ 30 years ago, then got weaker.) We might see Terokk, too. (I wonder what these new winged Arakkoa look like.)
But at least most of the other characters from BC came to Outland after the shattering, so not much room for rehashing.