Windows 10 is being released on July 29, 2015 according to article today at USA Today.
Windows 10 to arrive July 29 Internet Explorer is not part of the Release. (Replaced by "Edge").
Interestingly this just appeared on my desktop..and anyone who is up to date with Windows Update will now see the Windows 10 logo in their taskbar, and clicking it results in the attached (click to enlarge)
(Only applies to those with fully updated Windows 7 SP1, Windows 8 and 8.1)