I'm not sure how I feel about it, to be honest.
Draenor definitely has some massively frustrating areas to traverse. On my characters, when I go after rares or treasures on the map, I sometimes spent 10 to 15 minutes trying to find a way up, or in, or down, or whatever. That's a lot of time spent aggro'ing mobs and falling to my (near) death.
But, I do kinda like not having to buy a flight license again. I'm really tired of the whole "oh, your flying mounts lost their brains -- throw some money at this random NPC to "fix" it." I mean, I know they do it partly as a gold sink, but I kinda don't like sinking gold into this thing.
The problem is that, if they do add flying, something about the expansion will require it. TBC required it for Netherstorm (which was obviously built on the expectation you'd be flying) and the Ogrila dailies. Wrath required it for Storm Peaks and Icecrown (same problem as Netherstorm) and for the Icecrown dailies to access the airship. Cata required it because getting around in the world was a miserable experience without it, and Deepholm seemed to required it in general and for the airship. MoP neeeded it for the Halfhill dailies with the charging rams of doom (thankyouverymuch for the falling death, uh huh uh huh).
It's pretty obvious that they can't make the work meaningful on the ground when flight is an option. Or, maybe, they just don't know how. I'm not sure.
But, I'm on the fence. If they add it, I'll begrudgingly pay the fee to fly at 310% rather than ride at 100%.
One thing I would like -- faster ground mounts.
I bet they can't really do that either. Rift has 165% ground mounts (no flying there) and they had so many geography problems they actually took out falling damage. You could literally DIE on flat ground because your ground mount would hit a pebble, fly through the air, and then you'd die.