Just a few minutes ago at the Worldwide Partner Conference in Toronto, Tami Reller from the Windows Product Group announced the Release to Manufacturing (RTM) and General Availability of Windows 8 the 1st week of August and late October respectively.  More details can be found at the following post.

http://windowsteamblog.com/windows/b/bloggingwindows/archive/2012/07/09/upcoming-windows-milestones-shared-with-partners-at-wpc.aspx

Enjoy!