Microsoft didn't choose Windows 9 as the name of the next version of Windows, instead it went for Windows 10, which is still better than say, Windows TH but we're still very much surprised by this apparent snub at the number 9.
Windows 10, we now know, will be cross-platform, absorbing Windows Phone (confirmed) and possibly Windows RT, Windows Server and Windows Embedded. In other words, this version of Windows is more than a mere evolution of Windows 8.1, which Windows 9 was supposed to be.
Veteran Microsoft journalist, Mary Jo Foley, sums up why Microsoft chose 10: "they wanted to signify that the coming Windows release would be the last major Windows update." while Microsoft's official stance, from Myerson is that "when you see the product in your fullness I think you'll agree with us that it's a more appropriate name".
In other words, that version of Windows is likely to be the last with a suffix; expect Microsoft to stick with Windows alone and potentially extend this naming strategy to the rest of its other brands (Office, Xbox etc) as it wholeheartedly embraces and extends the "as-a-service" paradigm to the jewel in the crown: Windows.
One cannot however ignore the fact that there's another operating system that carries a number 10, that's right, Apple's Mac OS X is in its 10th iteration (hence the X). Whether or not the naming convention is a subtle finger waving exercise at Apple, no one knows.
Before Google and Apple, Microsoft is the first to finally come up with a unified operating system strategy, the fabled one OS to rule them all. 2015 is going to be one of the most interesting in a decade as I expect both Microsoft rival to finally merge their mobile and desktop operating system.