Yes because what the game clearly needs, where both varieties of Elf are among the most popular choices in the game...in the wake of an expansion that added a class restricted to elves only...is one new race of Elves and one outright theft of an existing Horde race for Alliance players who don't want to play with the savages but like the pretty white skinned elves.
Everyone in fact should reroll Elf.
Even the Legion, all the Demons should be swapped out with different kinds of Fel Elves.
As to the question at hand, I believe the only two races they haven't added that at some point in the past they said they would like to are Naga and Ogres. Those are my dream races for the next expansion. And let's be frank, next expansion is going to be a new race(s) because it's been so long since we added a new one and they aren't going to add a new class so soon after Demon Hunters.