I think this has potential to be the next great expansion since Wrath.
The fact alone that there is a 10-level increase instead of 5 levels makes me ecstatic. This leaves more room for storytelling and lore-immersion, especially in Draenor.
No flying for a patch won't be game-breaking or kill anybody. It'd be great to dust off my ground mounts and use them more, and I'm sure Blizz wont make the mistake of making everything too distant from each other so it becomes a drag.
The exclusion of new races/new classes is actually a great thing FOR NOW. It helps me create more of a connection to my characters instead of making an entirely new one because of a new expansion. 10 more levels with my veteran characters is going to be great.
However, my only fear is the end-game. I hope they learn from Cata and from MoP that grinding tedious heroics and doing dailies for a long span of time to just be raid-ready is not the way to go.