If it's due to business reasons it may be completely out of their hands. They are likely following a pre-determined patch schedule given to them by the big guys. (I can see why, as releasing it at a later date will pull in a new wave of players. Whether that is fair to current players or not... *shrugs* Up to the individual to decide.)
Also, to whoever said they want to play Warlock because it'll be OP on release... The adjusted version will be releasing on NA/EU. They'll probably wreck in PvP for awhile because people won't know how to handle them, though. I foresee complaint threads. :P
I do plan to roll a Warlock when it comes out, but I still have a lot of other classes to level (I like alts).