Microsoft communications chief Frank Shaw said the company wasn't ready to talk about how often Windows might come out when we spoke to him in January, but he agreed "you have certainly seen across a variety of our products a cadence that looks like that; Windows Phone is a good for example of that, our services are a good example of that".
We don't know if Windows 9 will be available as an upgrade from Windows 7 that you can buy as a standalone product or if you'll have to have Windows 8 to get the upgrade. But it may not be with us for a while yet - Windows business chief Tami Reller has talked about "multiple selling seasons" for Windows 8, meaning that we'll likely have several versions of it.
Some rumours have suggested late 2014 or early 2015 for a Windows 9 release, though the former seems wide of the mark.
In January 2014, well-known Microsoft blogger Paul Thurrott said he believes the company plans to release Windows 9 (codenamed Threshold) in April 2015, less than three years after Windows 8.
The thinking appears to be that the Windows 8 name is now too tarnished and that - in contrast to Reller's comments above - Microsoft wishes to clear things out by releasing Windows 9 instead.