You’ll need Windows 10 to run Microsoft Office 2019
Thursday, February 1, 2018 at 11:38PM 
With Microsoft Office 2019 set to come out in the latter half of the year, Microsoft made an important announcement about the productivity suite. The latest version will need users who aren’t subscribed to Office 365 to have machines running on Windows 10. Obviously, this move is the company’s attempt to get businesses to subscribe to its Office 365 business. They have even extended support for Windows 10 enterprise and education customers running versions 1511, 1607, 1703, and 1709 an additional six months to update to the latest supported versions of Windows 10. The support lifecycle for Office 2019 is changing, too. It gets five-year mainstream support and “approximately two years of extended support.”
Office 2019 will include Word, Excel, PowerPoint, and Outlook client apps as well as server versions of Exchange, SharePoint, and Skype for Business. Preview copies are going to be released in the middle of 2018. The software is intended for organizations that aren’t using the cloud Office 365 versions. It must be noted that Office for Mac won’t be affected by this change as it’s a different product with its own release schedule.
Source: The Verge