According to a rumor from Kaputik, Diablo III is expected to be released on Christmas Eve. Associates working on the Diablo 3 game design has supplied the following information:
The release date for the online beta multiplayer trial version is currently set to:
11th September, 2009
The final version, available for purchase is to be released before Christmas:
24th December, 2009

The system requirements are likely to be:
PC:
Operating System: Windows XP/ Vista
Processor: 1.4GHz or higher CPU.
RAM: 1Gb or more.
Video: 128Mb video card Dx9
Hard Drive Space: 4-8GB
Mac:
Operating System: MacOS X 10.3 (Panther) or better.
Processor:1.6GHz or higher.
RAM: 1Gb or higher, DDR RAM recommended.
Video: 128mb ATI or NVIDIA video card
Hard Drive Space: 4-8 GB

The information has yet to be confirmed by Blizzard. In the past, there has been many rumors of Diablo 3 being released on 9/9/09 but that was confirmed fake. Lets hope this rumor is a real release date.
Source: kaputik