It’s their last real kernel instantiation. They’ll basically be updating the Windows 10 kernel ad infinitum. It speaks to one of two things:
1) Redmond finally gets it
2) Someone’s making lofty promises
They’ve locked the kernel down pretty tight since Server 2012/Windows 8. If 10 is an extension of that PLUS they’re doing away with legacy x86 support, it could truly be the last time they need to create a new OS from the ground up.
Just like MS-DOS 5.0.
I’m typing this on an x86 computer running Windows (NT) 10 RTM.