I'm not too sure on that. There's a few reasons my subbed lapsed in MoP
At the very least there's GW2 which seems to have something similar to WoW's "dailies" available tot he players from level 1 and can be completed in almost any region of the game world. Someone correct me if I'm wrong, but are the daily/monthly thing in GW2 is something similar to the daily/weekly caps in WoW? Karma being used in a manner similar to JP and VP?It would really be great to have a reason to go back to the old zones as well... But the question is, does any MMO remain with old zones relevant after the coming of new content? And I am really asking, I don't know if there is.