I want to see more things regarding Lordaeron. I want Kul Tiras to finally be introduced into the game and a continuation of whatever Stromgarde story there is to be picked up on. Sons of Lothar are another thing I'd like to see get some attention.
I'd also like to see more of Rexxar, Rokhan and some more of that proper Horde squad. Ogres and trolls need to have their roles in the Horde expanded.