NOTE: Since Office 365 has undergone significant changes by Microsoft in it's naming convention and update channels, we will no longer be updating this post, as we have created a new post detailing those changes, and that post will receive the updates for new releases and EOL dates.
However, this post will remain to keep a record of the historical information on Office 365.
On April 20th, 2017, Microsoft announced that it will make big changes regarding Office 365 ProPlus.
The first part of the announcement detailed new system requirements, such as the need for all Office 365 ProPlus and Office perpetual in mainstream support to be connected to Office 365 services by 2020. However, the second part of the announcement created a much bigger stir among IT professionals: Microsoft has aligned the Windows 10 release schedules and support lifecycles with those of Office 365 ProPlus because customers have "asked us to simplify the update process and to improve the coordination between Office and Windows."
In February of 2018, Microsoft also announced clarifications to the Office and Windows servicing position. The first is for users running ProPlus in a Windows 10 environment: ProPlus will not be supported on Windows 10 Semi-Annual Channel versions that are no longer being serviced. The second clarification, effective January 14, 2020, is that ProPlus will not be supported on the following versions of Windows: Windows 8.1 and older, Windows Server 2016 and older, and any Windows 10 LTSC release.