Just to note, I believe alpha already has this:
Obviously its not 100% perfect since we dont currently get the ghostly white hair like Alleria’s but it seems like Blizz is making efforts in this area.
I do hope though that we get glyphs for it so people who like the old void form can still have it. More options are better!
Disclaimer: I am not in alpha so I did not take this screenshot. I have no idea if this was simply photoshopped but it came with other pictures that seemed legit.