Although i really dislike how Annie Mee exposes his argumentations, he does have a point. Winged flight is indeed wanted by the majority of the community, so much that it was one of the most popular questions during the Demon Hunter Q&A with LeCraft.
Here's a link for you:
https://youtu.be/2PdvE0ye7AE?t=40m31s
LeCraft's reasons for not implementing it are mainly lore calls, which can or cannot be agreed with (in my case, i think they sound a little weak. Illidan DOES indeed fly, it's mentioned often in the books aswell as pictured very clearly in the Harbinger series: if that is not flying, i don't know what else can be. But he's also supposed to be more powerful than a regular DH).