In Wrath of The Lich King, they added a new class and a couple of new professions, but no new races. There has been a rumour floating around for awhile that they are going to be adding new races in the next expansion, and a few days ago an inside source in Blizzard leaked a bit of information.
Naturally there is no way to confirm the accuracy of this information, but the last couple of similar leaks turned out to be accurate. If this one turns out to be true, then the two new playable races will be Goblin and Worgen.
Horde side will get saddled with shrill, annoying (though sometimes amusing) Goblins.
Alliance will (once again) get the cool, cute ones.
If this goes down, it will be twice in a row where the Horde gets screwed. As much as I detest almost everything Alliance in this game, if I am still playing when the next expansion comes out, I will seriously consider using one of the (rumoured) faction changes. As usual, Alliance gets all the best stuff.
Well maybe I won't move all of my characters, but I'll delete my Blood Elf paladin and create a Worgen for sure. By the way, my new avatar is what my priest looked like for an hour or so after an engineering transporter accident. While I kinda miss the bondage straps across the face, at the same time you have to admit that she makes a pretty cute Draeni.