With Windows 8.1 out in the wild Microsoft has already started work on the next major milestone for the operating system. The update is being called "Threshold" internally – named after a planet in the Halo universe – and marks another step in the company's paradigm-shift toward rapid-fire maintenance releases and platform homogenization across its latest generation of products and services.

ZDNet's Mary Jo Foley cites multiple anonymous sources and an internal Microsoft email from executive vice president Terry Myerson as confirmation for the codenamed project. More importantly, Foley says that Threshold will include updates to all three platforms – Xbox One, Windows and Windows Phone. These already include a common Windows NT core but the update moves further in that direction to share even more elements.

Microsoft reportedly plans to unify the developer toolset for all three of the platforms and support the same core set of "high value activities" across platforms. These include expression/documents (Office), decision making/task completion (Bing), IT management (Intune), and something labeled as "serious fun".

The move would be in line with the company's desire to become "One Microsoft," with apps that work across platforms and only have to be purchased once, and a single app store to house them all.

As it stands right now, the Windows Store offers 'Metro' style apps for Windows 8 and RT, and though many of them will run on both x86 and ARM architectures, not all of them do. Then there's Windows Phone, which is also designed to run on ARM processors, yet apps built for Windows Phone won't run on Windows RT.

Before Threshold arrives, however, Microsoft is reportedly planning an update to Windows 8.1 (known as Windows 8.1 Update 1) along the release of Windows Phone 8.1 (codename Blue) sometime in 2014.