There's been a lot of speculation lately about the next expansion being about the Burning Legion (which would be nice). It would be nice if they also, as the chatter suggests, redid Outland. But I see one logical problem there.
Outland should be dead and destroyed by now. The water is running off, the atmosphere should have been leaking away. It's been (lore-wise) how long since the campaign against Illidan there? Going through the Dark Portal now (assuming it is still supposed to actually be there) should result in a person finding themselves on a dead, airless rock.
I don't care how much magic was there. Nothing short of Titan magic could save that chunk of Draenor from eventually dying, and I wouldn't even count on that.
Of course, it might be fun to see Arrokoa refugees running about Org/SW. Maybe make them playable? But, ugh, Allies would get them, and Horde would probably get those godsawful ugly, brain-dead ogres.