Microsoft has targeted availability of Windows 8 for the end of October as noted below:

Windows 8 – October 2012 Release Announcement

QUOTE: Speaking at Microsoft’s Worldwide Partners’ Conference in Toronto, Tami Reller, the CFO of Windows and Windows Live, said that consumers can get their hands on the product by the end of October. The software, she explained, will release to manufacturers (RTM) during the first week of August. Microsoft is busily adding flesh to the bones of its Windows 8 strategy. Last week, the software giant confirmed that it will cost users just $39.99 for Windows 8 Pro if they upgrade from a previous version of Windows.

Windows 8 Team Blog – October 2012 Release