It's pretty funny how the Barrens right now have Deathwing's lava, Garrosh's goons running around and turning the elements inside out, and the Burning Legion sprinking fel fire on top. What's next, the return of Barrens' chat?
About the zone update... not happening. As much as I'd love seeing the cata destruction scarred over, it would take way more than a fresh coat of paint and a few more drops of water in Loch Modan. Zone geography is tied to the quests (as they're mostly Deathwing-related), and they're not making dozens of new quests for updated zones because it's a giant resource drain for no gain at all.
And they can't let you play in the "old" zones because they were never intended for flying, so it's all smoke and mirrors and props and invisible walls, and removing them was a big part of the Cataclysm revamp (and one of the big reasons why we're unlikely to ever get flying in Quel'Thalas).