Blizzard has removed flying for at least the first major tier of WoD. We all know that. Several people complained about this, but most are in favor to have this change, and also most want it for the entire expansion.
That being said, what if they implemented a fast travel, or instant travel system? So as long as you got the "waypoint" in that zone, or "waypoints" you could instantly portal there (with a short cast time) from where you were based off the map, paying a little gold in the process?
Kinda like how Diablo 3 works with the bounty system. You can pretty much teleport to any waypoint, or player that you choose. But in WoW you would have to discover the waypoint first, or perhaps they could do a little quest event to unlock each new waypoint you encounter.
You would still have your mounts, and you could still travel with them (on the ground) if you so choosed, but you could take the convenient way through fast travel if you wanted as well.