Well Vista , 7, 8,8.1 and 10 seem very similar anyway ,so I think Microsoft stopped making new OS’s long ago
There isn't enough programming talent on Earth - architects, developers, code monkeys - to make a new OS from scratch, in a reasonable time frame, that would be anywhere close to existing Windows and Linux.
Microsoft is forced to only do small improvements in the OS. They tried - and failed - to make larger changes, like the new filesystem. (The NTFS is with us since Windows NT - since 1990s.) The changes that MS is touting with every new release are superficial, and largely insignificant. Take the Aero Glass, for example - it is a nice feature, but it does not add or remove functionality, compared to XP. Or take much faster startup/shutdown on Win8/10 - it is nice on laptops, but it has no effect on always-on desktops in businesses.
I don't want to guess why and who said what about Windows 10. That talk is not worth anyone's time, as Microsoft on numerous occasions had said one thing and then circumstances led it to do another.