Starting on March 26, 2017, the first release of Windows 10, known as build 1507, will receive no further security updates. This is part of Microsoft's strategy to limit support to two Current Branches for Business of Windows 10.
So basically, to continue to receive security updates after March you or your business will need to be running the Windows 10 November Update (build 1511) or preferably the newer Anniversary Update (build 1607).