I will begin by stating that the idea of 'class balance' in a game that at its core is a single player experience seems ridiculous. It would seem that adding pvp to the game will give them a permanent excuse to constantly buff and nerf classes in the name of supposed 'balance.' I find the volume of class changes that occur during any given expansion of WoW to be completely obnoxious, and I believe they do this on purpose to impose some sort of synthetic level of class representation.
So will the future of D3 just be the same old carousel of rotating flavor of the month classes, the type of thing that drives players crazy who would prefer to not having Blizzard mutilate their chosen class with every patch?