I hope that the following is reasonably accurate summary of the articles I'll cite at the end:
New CPUs will require Windows 10 [or the then-current Windows O/S, if they ever release a new version]: Windows 10 will be the only supported Windows platform on Intel's upcoming 7th-generation "Kaby Lake" processor (to be released in 2016).
NEW consumer-based Intel 6th-generation Skylake devices must run Windows 10 to be supported.
A select list of NEW enterprise-based Intel 6th-generation Skylake devices will support Win7 or 8.1 for a period 18 months, until July 17, 2017, after which those enterprise customers will be expected to upgrade to Windows 10. Post July 17, 2017, Microsoft will address only the most critical Windows 7 and Windows 8.1 security updates on Skylake devices. Furthermore, these updates will be released only if they do not risk the reliability or compatibility of the Windows 7/8.1 platform on older devices.
Fortunately, older Intel 4th-generation Haswell and 5th-generation Broadwell CPUs will continue to be fully supported for the announced life-cycle of pre-Windows 10 operating systems: Windows 7 (currently in the Extended support phase) will continue to receive updates until January 14, 2020, and Windows 8.1 will be supported until January 10, 2023.
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Sources:
http://www.zdnet.com/article/microsoft-updates-support-policy-new-cpus-will-require-windows-10/
https://blogs.windows.com/windowsexperience/2016/01/15/windows-10-embracing-silicon-innovation/
http://www.zdnet.com/article/new-microsoft-windows-support-changes-what-they-mean-to-business-users/
http://news.thewindowsclub.com/microsoft-urges-enterprises-upgrade-windows-10-81591/