Windows 10 version 1511 End of Support: : October 10, 2017
Windows 10 version 1511 will no longer receive security or quality updates after October 10, 2017.
What this means?
After October 10, 2017 Windows 10 version 1511 will no longer receive security or quality updates!
Why is this important?
Because many customer began to deploy Windows 10 and may have no plan to update these machines. With the new Windows as a Service cadence, this will happen every 6-8 months with every version moving forward. Dell has several services that can help them develop a plan for updates. —
Microsoft announcement can be found here