We have reported earlier that Microsoft would be previewing a pre beta version of Windows 8 at worldwide partners conference which is scheduled to be be held from July 10 to July 14 at Los Angeles ,today two independent sources conformed the same. Further mswin is reporting that Microsoft would start working on windows 8 beta branch from July 14 exactly after WPC 2011.
According to more information available Microsoft would be releasing Windows 8 pre beta to Microsoft gold partners just after WPC 2011.
It has already been confirmed by multiple sources that Microsoft would be releasing Windows 8 beta during Build conference which is scheduled to held in September. Further according to rumors the RTM version of Windows 8 would be released in April 2012.