Microsoft has confirmed that the Windows 8 Release Preview will arrive in the first week of June.
The announcement was made by MS WIndows President Steven Sinofsky at the Windows 8 Dev Days event in Japan and simultaneously broadcast on Microsoft's official BuildWindows8 Twitter feed.

The Wndows 8 Release Preview will replace the current Consumer Preview and should be the final stage before the official product is released.
Windows 8 is a significant departure from Windows 7, with a much stronger emphasis on touch integration courtesy of the new 'Metro' tiled interface. Improvements over Microsoft's previous OS include a faster, more streamlined browser (in the shape of Internet Explorer 10), deeper customisation, improved multi-monitor support and the ability to connect to your data and settings wherever you sign in with a Microsoft account (read more here).
Microsoft has previously announced that it will launch three editions of Windows 8: Windows 8, Windows 8 Pro and Windows RT. (Tablets, desktops and laptops using Intel/AMD x86 processors will be available under the Windows 8 and Windows 8 Pro brands. Windows RT, meanwhile, will come pre-installed on ARM-powered devices.)
We'll keep you posted with a concrete release date for the Windows 8 Release Preview. Watch this space.