In a pretty startling change to established policy, Microsoft has announced that PCs based upon new architectures (including Intel's Skylake) will require Windows 10. Support for Windows 8.1 and earlier on new hardware will be limited or not available at all.
Windows 7 is still being supported by Microsoft through 2020 as before, but only on existing hardware, which is not how things worked previously.
ComputerworldThe way it's always been in the past is that enterprises could buy today's hardware, but put their current image on it, only upgrading when it made sense. But with this move, Microsoft changes everything -- and with precisely zero warning.