Just to add to this and...rain on the parade for those wanting non-humanoid races. They will not add a race that is anything other than a bipedal being with an upright posture and two upper limbs and a head. The simple reason being their gear models. If you added a quadruped, you'd have to completely redo a huge amount of gear. Not only that but there are lore reasons, as at least one poster has mentioned.
However, I'll go back to the reason I was talking about. The ability to relate to a new race in a game such as this is important. There is no question that some players would have no problem identifying with whichever type of playable race takes their fancy, be it beastly, electronic or biomechanical, with 4 legs, 2 legs, wheels or thrusters. However the vast majority of players will not identify with such playable races. If you take into account the significant amount of effort a new race requires along with the marathon task of modifying the gear models, which would be even more for 'different' races, I just don't think it's possible to make a case for such a playable race. The same thing goes for races that do not heavily feature handsome males and pretty females.
Generally speaking heroes are handsome/pretty, charismatic characters. I frequently see people wondering about a new race that would be conventionally speaking, considered unattractive, beastly, and generally speaking unsympathetic. Such races would be so niche as to make even the rarest female Roegadyn look popular.
What we need is not another race (though cute/handsome humanoids with white wings and a noble disposition would not hurt the game IMHO...), rather we need one or two additional faces (and features) for all current races to give a bit more variety and flexibility to character design.
Glaring needs for existing races....eyebrows for Highlanders, Highlander females need better complexions, both Au'ra and Miqo'te females need a face that looks old enough to vote and drink...