Nothing got named "Windows 9" because Microsoft feared compatibility issues with janky programs looking for the first set of characters in "Windows 95" or "Windows 98."
Later this was changed by the marketing department to some blather about "wanting consumers to perceive a clean break from the previous version." But then, Microsoft also claimed Windows 10 would be the Last Windows, and it would just have feature updates built on top of it forever as a service. So you sure as fuck can't take anything they say at face value.