Naga for the Horde. It would work as the Worgens, the players could change between Naga and Highborn form (To use mounts since it would be hard without legs).
A group of rebel Nagas who with the help of the Blood Elf Mages managed to weaken the curse of the Old Gods, allowing them to walk in the highborne form once again, even not permanently...
Few years ago I would say Pandarens for the Alliance, but MoP trolled me >< And now I really don't know what race would fit in the Alliance...Some kind of Vyrkul or Ethereals, maybe?
Orges just fit the horde.
Not sure about the Alliance though. IMO much tougher to find a new race and still keep the Alliance feel.
I did find it interesting that Or'Dac a Brackenwall Emisary was at Domination point. Misdirection maybe, but I still feel we have an impending burning crusade expansion coming next (I was very wrong about mists... even after the name was leaked).
Naga naga naga naga naga naga naga naga... did someone say something about Naga because they're the best race, by the way. Also, Naga.
Soothing Mist:"Healing them for a minor amount every 0.5 sec, until you take any other action."
Jade Serpent Statue: "The statue will also begin casting Soothing Mist on your target. healing for 50% as much as yours. "
[What's half of minor?]
"Statue casts Soothing Mist at a nearby ally for toddler healing."
Considering that next expansion will be legion focused and take place in other worlds i would love to see 2 completely new races. On top of that it would be lovely if they joined in higher number than 7 (im looking at you panda's !!!) and lacked typical to WoW "90% of race was slaughtered by <insert hostile force here>". It would be nice to have races that would be really powerfull on they own and rather than joining alliance or horde would ally with them as equals.
i actually quite like the idea of changing between naga/highborn, would solve most of the issues like how will armor work on them, mounts etc. maybe naga form will have to be a bit like druids forms and not all armor show on them.
but for horde i see ogres being the best choice, seeing as they were already part of the horde for a while. playing as one of rexxars people would be cool, i forget the name of them.
i want to play as a harpy so badly T.T
Soothing Mist:"Healing them for a minor amount every 0.5 sec, until you take any other action."
Jade Serpent Statue: "The statue will also begin casting Soothing Mist on your target. healing for 50% as much as yours. "
[What's half of minor?]
"Statue casts Soothing Mist at a nearby ally for toddler healing."
These would be my top 2 choices. Naga and ethereal.