Quote Originally Posted by Lemuria View Post
Two major differences here. Firstly, in WoW the cap is a hard cap. You literally don't even unlock the ability to level past your cap without the expansion. Secondly, in WoW, once the level cap is 'earned' by getting the expansion, you can still earn experience in earlier areas. It's not like all of your new levels had to be earned in expansion areas only.
Why, if you have the expansion, would you want to level in the older zones when you have access to the new zones? Also the amount of XP needed will scale higher from 50-60. So could as easily take 100,000s of mobs in the 2.x zones to even get to 51, then xp from mobs will be less as you level requiring exponentially more kills.