Blizzard already "introduced" the new female Draenei model a while ago, but as you might have noticed, it was just an April fools. Keep in mind that the model is still a work in progress, and currently it does not have any animations to pose her body or face.
Animation is really a crucial factor for the Draenei female model, so it's important to keep it in mind when comparing these two. The old female model has some fairly extreme posing that happens when she's animated. If you were to see the static model of the original without any posing, you'd see thatit looks very similar to the new one. With her pose applied her shoulders stretch backward, her pelvis rotates forward, and her chin lowers, causing her head to angle downward. The curvature in her lower back, and why the head shape looks slightly different, are also due to the new model not having the same posing applied yet. She also looks a lot taller. Ultimately, all of these thing will be addressed when the new model will be animated. The animations are done only after she's rigged and sent on to the animation team.
The Draenei model as you can see looks more detailed compared with the old one. I hope we'll get to see some anymations soon™.
Blizzard stated that Draenei and Blood Elves have the lowest model update priority. Their models will be updated only, once they update all the Vanilla races' models.