Windows 10 is different in many regards to previous versions of Windows. One core difference is that it marks the move from releasing a new version of Windows every three or so years to Windows as a service.
What is meant by that is that Windows will follow the same model that Office 365 and other SAAS products offer. Namely, that there won't be a Windows 11, 12 or One, but only Windows 10 that is constantly updated.
Microsoft released two feature upgrades to Windows 10 so far. The operating system itself was released on July 29, 2015, and the two feature upgrades in November 2016 and in July 2016. The first upgrade was called the November upgrade, the second the Anniversary upgrade.
The company plans to release a third feature upgrade, called the Creators Upgrade, in Mach 2017.
This rapid release scheme poses issues for Enterprises, as they have to cope with the new situation. Along with the faster pace in which new versions of Windows 10 are released comes a major change in how long these releases are supported.
Windows 10 PCs used in professional environments fall mostly in the Current Branch for Business (CBB) support model.
Windows 10 Home versions, and most Windows 10 Pro versions used by individuals, fall in the Current Branch (CB) support model mostly. This means that feature upgrades are made available right away after they are released.
If the operating system's automatic update mechanism has not been modified by the user, these upgrades will find their way on consumer PCs quickly after release.
Businesses may defer upgrades. This enables the Current Branch for Business support model for PCs which delays the release of feature upgrades for about four months.
End of Support
End of support for older versions of Windows 10 comes also more rapidly. Microsoft stated earlier that it wants to support two CBB releases at any given point in time. This means that support is dropped for the CBB release prior to that with a 60 day grace period).
The initial release version of Windows 10 was declared a CBB release right away.
The current CBB release is the Anniversary Upgrade released in July 2016, the previous CBB release the November Upgrade, released in November 2015.
Remember, it takes four months for a feature upgrade to become the current CBB of Windows 10. This happened for the November Upgrade on April 8, 2016, and for the Anniversary Upgrade on November 30, 2016.
This means however that the first release version of Windows 10, version 1507, will no longer be supported by Microsoft 60 days after the second feature upgrade was declared the CBB by Microsoft.
When Windows 10 version 1507 reaches end of support, it won't receive any more updates, security or otherwise. While it will continue to work for the time being, it puts the version of Windows 10 in the same shoes as Windows XP or any other Microsoft operating system that reached the end of its support lifecycle.
What this means for Enterprises
Enterprises, with the exception of those on the Long Term Servicing Branch, face a rapid release cycle that will see Windows 10 versions being dropped much quicker than was the case for previous Windows releases.
Microsoft plans to release two feature upgrades in 2017. The first will come out in March 2017, the second probably in the August to October period.
The March release of the Creators Upgrade, and it becoming the CBB in July 2017, means that the November 1511 feature upgrade will reach end of support in September 2017. The current major version of Windows 10, the Anniversary Upgrade, will be dropped in early 2018 shortly after the second feature upgrade of 2017 becomes the CBB.
Greg Keizer over on InfoWorld suggests that Microsoft will drop support for Windows 10 1607 around April 2018.
Things are delayed a bit right now as Microsoft released only one feature upgrade in 2016. The pace will increase after 2017 when two feature upgrades get released.