The title should be changed. Windows 10 will only support Kaby lake and not earlier versions. It's not that it is impossible for Windows 7 to support Kaby lake it's just that Intel and Microsoft have decided to not to add the support in earlier Windows versions. Microsoft for example do everything in order to force people to Windows 10.
Microsoft, Intel and AMD made it clear, that earlier Microsoft platforms before Windows 10 will not be supported anymore on next generation silicon. This could lead to Skylake-hardware being in high demand for the foreseeable future.