The name 'Threshold' has been used to refer to the next major update to Windows for some time. The name, which is widely believed to be the codename for the project, is getting much more official thanks to a posting on a LinkedIn profile.
We did censor the post a bit as we imagine that Microsoft won't be too pleased that one of its program managers has publicly acknowledged working on the unannounced project but you can clearly see the posting above. While no new features are stated on the page, it adds to the credibility of the information that has been doing the rounds for some time.
The latest bit of information about Threshold is that its development is on track for a launch next year, and you should expect it to show up around spring 2015.
Microsoft is working on more than just Threshold, as Windows 8.2 or Update 2 is approaching release. It is expected that this next update to Windows will arrive around August but, based on current information, it doesn't look like that build will feature the return of the Start menu.
Microsoft first showed off the Start menu at Build 2014 but so far, has not provided any update on when it will make its big debut back on Windows.