Microsoft plan to retire a 2015 version of Windows 1511 on April 10th.
This version of Windows was set to retire on October 10th 2017 but Microsoft extended service for an additional 6 months at no cost.
Other versions of Windows 10 that will receive an additional 6 months monthly service updates after their end of service date include 1607, 1703 and 1709.
- Windows 10, version 1607 has an end of service date of April 10th 2018
- Windows 10, version 1703 has an end of service date of October 9th 2018
- Windows 10, version 1709 has an end of service date of April 9th 2019
If you would like to find out more information on Windows life cycles, Microsoft have a fact sheet found here.