Remember when Blizzard told us all that Diablo III as a "console interpretation" would not lead to the PC version of the long awaited title slipping? It's slipped.Today, Mike Morhaime, CEO and cofounder of Blizzard Entertainment siad, "The beta test is going very well, and
we look forward to making the most of the extra time we're taking to deliver an experience that lives up to our vision for the game and the expectations of our players. Next year is going to be an incredibly busy one for Blizzard, and we hope an incredibly fun one for Blizzard gamers." (Our italics)
The nearest he comes to a reason is, "we didn't put so many years of work into Diablo III to release a game that was almost ready."
Source:
Blizzard