"Microsoft Corp. is preparing Windows 10 for release on July 29, in time for the back-to-school personal-computer season, as the company tries to boost an ailing PC market and revive its own fortunes in mobile devices.Microsoft Readies Windows 10 for Next Month in PC, Tablet Push - Bloomberg Business
The operating system will be available for PCs and tablets as a free upgrade to people using Windows 7 and Windows 8.1, or on new Windows 10 devices, Microsoft said in a statement Monday. Windows 10 for other devices will be available later this year."
Monday, June 01, 2015
Microsoft Readies Windows 10 for Next Month in PC, Tablet Push - Bloomberg Business
Check this Microsoft post for more details