Originally Posted by Astor_Kaine
Now, this may sound cynical, but what's the betting that this is just Actiblizzard (or whatever they call themselves nowadays) wanting a quick profit?
They've probably sat in the board room and tried to decide what will make them a quick buck. So they decide to make a sequel to Diablo II. Based on it's popularity, they could grab any game and put 'Diablo' and 'III' and people would probably buy it.
Their historic says otherwise. Their games have gigantic developing and refining stages, which by their turn are subject to all kinds of push-backs and the company doesn't have any reservations from cancelling games on the later stages of developing (see Starcraft: Ghost
With all that said, I would highly doubt that's solely a market based release. Plus, why would they take so much time between the second and third installments?