- For Windows 10, Microsoft will continue its traditional 10-year support lifecycle. The five-year mainstream support phase begins with the release of Windows 10 on July 29, 2015, and a second five-year extended support phase begins in 2020 and extends until October 2025. (That's a few months later than July 29, 2025, because of the way Microsoft calculates support dates.)
- A note to that policy qualifies the support commitment to devices where the OEM continues to support Windows 10 on that device.
http://www.zdnet.com/article/microsoft-commits-to-10-year-support-lifecycle-for-windows-10/