Release date estimations

While no official release date has been announced yet for Diablo 3, there has been much speculation to a potential “ball park” figure on the launch date for the much anticipated title.
Vivendi revealed that the newest World of Warcraft expansion is due sometime in the fall of 2008. In addition, Starcraft II is also due out around Christmas.
So what does this tell us? Well, if anything it reveals a pattern of release timing. After the first announcement of each of these respective games their release dates were scheduled between 8 and 12 months later. This same scenario should hold true for Diabo III.
This would put the game’s release date between March and July of 2009. A release date during this time fame allows Blizzard’s other title releases to soak up all the economic benefit to further bolster the companies revenues for the 2008 fiscal year. With no current releases or expansions scheduled for the 2009 year, it would be a pretty bleak stock outlook for the company to not release a game before Q2, or at the very latest Q3 of 2009.
Source = Diablo 3 Zugg