When I blogged recently about Microsoft's plans on the operating-systems front following Windows 8.1 , I mentioned a couple of "spring 2015" releases.

It turns out the Microsoft codename for that wave of deliverables is "Threshold."

A couple of my contacts have confirmed that Microsoft Executive Vice President Terry Myerson recently mentioned the Threshold codename in an internal email about plans for his unified operating-system engineering group.

If all goes according to early plans, Threshold will include updates to all three OS platforms (Xbox One, Windows and Windows Phone) that will advance them in a way to share even more common elements.

(The codename Threshold, for those wondering, derives from the planet around which the first halo ring orbited in the original Halo game launched back in 2001. Threshold joins "Cortana," Microsoft's answer to Siri , as yet another codename with its origins in the Xbox franchise.)

From what I've heard, Threshold doesn't refer to a single Windows OS -- not even the expected, converged hybrid comprised of the Windows Phone OS and Windows RT . Instead, the codename refers to the wave of operating systems across Windows-based phones, devices and gaming consoles.

The Xbox One OS, Windows 8.x OS and Windows Phone 8 OS already share a common Windows NT core . As we've heard before, Microsoft is working to deliver a single app store across its myriad Windows platforms. Company officials also are laboring to make the developer toolset for all three of these platforms more similar.

But Threshold will add another level of commonality across Microsoft's various Windows-based platforms, sources said. With the Threshold wave, Microsoft plans to support the same core set of "high value activities" across platforms. These high-value activities include expression/documents (Office, and the coming "Remix" digital storytelling app , I'd think); decision making/task completion (Bing, I'd assume); IT management (Intune and Workplace Join, perhaps?) and "serious fun."

CEO Steve Ballmer mentioned this concept of high-value activities at back in July when he announced Microsoft's cross-company reorg to make the company more focused around its new "One Microsoft" mission .

Before Microsoft gets to Threshold, the company is on track to deliver an update to Windows 8.1 (known as Windows 8.1 Update 1) around the same time that it delivers Windows Phone "Blue" (Windows Phone 8.1). That's supposedly happening in the spring 2014/Q2 2014 timeframe, from what my sources have said.

I've asked Microsoft officials if they'd confirm any of this information about Threshold. No word back so far.

Update: A Microsoft spokesperson said the company had no comment on "rumors and speculation."