This morning at the Worldwide Partner Conference in Toronto the Windows Product group announced Release to Manufacturing (RTM) and General Availability of Windows 8 the 1st week of August and Late October respectively.

Check out the post:

Windows 8

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

Windows Server 2012

http://blogs.technet.com/b/windowsserver/archive/2012/07/09/windows-server-2012-final-release-timing.aspx