Problem with Cata was limited resources - Blizz had to focus both on remaking old world and making new zones and raids - that's why they failed in both. No chance they will make this mistake again, and what's the point? If you want some good leveling experience you can go to Classic - wow was always about pvp/raiding. Next xpac will be just another island/world - maybe Void Lords domain. I don't say it's smth bad - it's just another xpac, no worse and no better that others. Another grind - maybe a trinket with levels? Don't wait for a miracle, Blizzard could do it, Activision - can't.