Vieras are far far FAAAAAAAAAAAAR superior to the miqo'te and they always will be. However, as many have stated, they do not belong in this world. New races, however would be interesting. I don't think they should be added later on in the game, because people usually stick to one character their entire playthrough, so it'd be unfair to them. I dunno if SE has any plans for that in the future, but I doubt we'll see any new playable races. It'd be cool, however, to start in the Garlean empire, but that would give the game some terrible competitive vibe that WoW, TOR, and other games have and I'm not really looking for that.

Also I'm really not a fan of people wanting Square to shoehorn stuff from older FF games. Magiteck armor, jobs, etc. Whatever though.