Earlier this year, Microsoft announced that they would be shifting to monthly updates for Windows. While this move made sense, considering the new rapid release cycle, the company also shot down the rumors of Windows 8.1 'update 2'.
The confusion around the name of Windows Threshold was linked to the fact that those with inside sources, like Neowin, were hearing that the next major update to Windows would be called 8.1 update 2 or Windows 9. Because of this, we kept calling the next major update Windows Threshold, and not 9 or 8.1 update 2 as the signals were confusing. Now that Windows 10 is out, we have a much better understanding of the picture.
Windows 8.1 update 2 did exist, at least, internally at Microsoft. As you can see in the image above, there is a clear reference to the unreleased update that we likely now call Windows 10. This indicates that, at some point, Microsoft planned to deliver the Start menu to Windows 8 via update 2 but changed their minds and instead decided to include the menu in a brand new OS: Windows 10.