I mean, many races still lack HD resources: Dwarves, Gnomes (if we exclude Mechagnomes assets which are fairly different), Tauren (if we exclude Highmountain assets which are fairly different), Trolls (if we exclude Highmountain assets which are fairly different), Forsaken (not enough assets from Darkshore), Blood Elves... Don't get me wrong, I'm hoping all I can for a World Revamp for 10.0, but I am not holding my breath. I've been waiting for many years now, and with each announcement comes its fair share of disappointment.
That being said, a World Revamp done over the course of two expansions could work, that or zones being revamped every X patches and having their own independent story, joining the leveling rotation could prove interesting.