Windows 8 is approaching to the Beta phase. So, it seems we can expect an unveiling at the Microsoft Worldwide Partner Conference, and the Windows 8 M3 / Beta is expected to be offered to participants at the Professional Developers Conference 2011 in September 13-16, 2011, in Anaheim, California.
According to centrumxp sources indicate that build 7996 is now in testing:
the production of Windows 8 Beta 1 will last a minimum of 6 weeks to a maximum of about 3 months. And that would cover all of our previous assumptions that the first beta we look forward to as early as the coming holidays, and by September. It's worth mentioning that on 10-14 July will be held in Los Angeles, Microsoft Worldwide Partner Conference, where we expect to be unveiled Windows 8 in one of the complication is derived from Branch Beta.
This timeline appears to correlate with a leaked roadmap, indicating that Windows 8 Milestone 3 coding was to begin on February 28, 2011. According to Softpedia article, M3 coding should be wrapped up no later than July 2011 (for comparison, Windows 8 M2 took approx. 5 months from start to completion).
Unfortunately, it's possible that build 8000 may be just another build as Microsoft heads to beta:
It's critical to note that Windows 8 Build 8000 is not the fully-fledged Beta development milestone, but only one of the many Builds which will be created on the path to the actual Beta.
Windows 8 M3 Build 6.2.7996.0.winmain_win8m3.110429-1810 was compiled on April 29th, 2011, and in this regard, it's quite possible that Build 8000 was also wrapped up, or that at least, Microsoft is quite close to doing so.