According to sources at Microsoft, the company plans to ship Windows Vista Release Candidate 1 (RC1) in early September. More important, perhaps, is that Microsoft still plans to release Vista to manufacturing by the end of October as previously planned, defying rumors that the company would delay Vista yet again.
Although I'm not at liberty to divulge the full contents of the message, Microsoft has placed build 5520 into escrow as the RC1 of Vista. This build will be released to testers and the public after the Labor Day holiday in the United States, which falls this year on September 4. Currently, Microsoft expects to ship RC1 on or after September 7.
Meanwhile, the release to manufacturing (RTM), or final, version of Vista is set for a September 2006 escrow and final release on or before October 25. We can expect a Longhorn Server Beta 3 release in first quarter 2007, an RC2 release in second quarter 2007, and the final release in the second half of 2007.
News source: WindowsITPro