Microsoft’s Terry Myerson (Executive Vice President) announced that Windows 10 would be released globally sometime "this summer".
That could be as late as September 21st but still a month earlier than a typical Windows release date of late October. It will be available in 190 countries and 111 languages around the world.
Meyerson, who runs the Windows division, made the announcement at the WinHEC conference in Shenzhen, China, on March 18th 2015.
The earlier than expected availability date gives Microsoft and PC vendors less than six months to complete development of Windows 10, test and manufacture their new hardware models and be able to deliver it.
Microsoft’s free upgrade will no doubt be in the form of an Electronic Download file similar to when Windows 8 was first released.
Windows 10 Upgrade Paths. Take note that not everyone can upgrade via Windows Update and will need to obtain the .ISO file and use it to create an installation DVD or USB Flash / Thumb drive. Windows RT is “Not supported”.