This extra six months of support won't be offered to users of other versions of Windows 10 1511 (which Microsoft started rolling out to mainstream users in November 2015), officials said. That means Windows 10 Home, Pro, Mobile, and Mobile Enterprise must be on Windows 10 Version 1607 or higher to continue to get security and other updates.
Microsoft will make both "critical" and "important" security updates available to Enterprise and Education users running 1511 via all normal channels, including Windows Update, WSUS, Configuration Manager, and the Windows Update catalog.
Microsoft officials denied that this support extension is due to any particular problems users may be experiencing in moving from 1511 to a more recent release of Windows 10.
"Customers with large, complex IT environments are still transitioning into the Windows as a Service model," said a company spokesperson when I asked for reasons for Microsoft's latest support extension. "Our early adopter customers are actively moving forward and asked for a few more months to finish their updates."
"The supplemental servicing security updates are in response to enterprise and education customers with broad early adoption of Windows 10, who are actively moving to Windows as a Service, and are focused specifically to keep them compliant on 1511 while they finish their updates," the spokesperson added.
The successor to 1511, known as Windows 10 1607 -- which began rolling out in August 2016 -- is currently slated to be supported until some time in March 2018. Version 1703, which began rolling out in April 2017, is slated to exit support in September 2018, and the just-released Windows 10 version 1709, which began rolling out in October 2017, should be supported until March 2019.