I will never believe balance is as hard as they say it is. I dont even care if every class is 100% balanced. I dont recall a time when I wouldnt log on because some class was just so incredibly broken.
Of course Ford retires old models but they are still around arent they? They dont hunt them all down and scrap them when a new model comes out. A new class wouldnt be entirely new either. It will still be melee dps/ranged dps/tank etc.
I dont recall saying they should redo WoW from the ground up. I also dont see how adding new classes would do that.