Office 365 ProPlus customers can keep running older versions of Windows longer after a change of heart by Microsoft.
Windows 8.1 will be supported for Office 365 ProPlus through January 2023. That means both Windows 8.1 and Office 365 ProPlus now have the same end of support date for Windows 8.1.
Office 365 ProPlus will be supported on Windows Server 2016 until October 2025.
Of course, you’ll be able to run Office 365 ProPlus after those dates, but without support or fixes for security bugs.