The playable Horde needs a different name imo, they are way too reasonable.
When you hear the word, Horde, do you think a coalition of races that will more than occasionally join with outside forces to dismantle nasty beings, and consists of half peaceful races?
Or do you think of a pack of bloodthirsty, brutal warriors who seek to wipe out all in their way?
I think the latter is more fitting. I personally am hoping that Garrosh recruits the real Horde under Blackrock mountain, and also the Yaungol in Pandaria.
They are collectively the most hordelike creatures currently on Azeroth. All that's left is for the reinforcements of Fel Orcs and Demons to walk through the portals, and then we have ourselves a right mighty, and very nasty, group, which possesses exactly what Garrosh cares for most above all else, Strength.
Obviously though, the demons would be much, much later into the xpac, as there has been some hints towards a Burning Legion xpac next.