Microsoft will be releasing an update to Office for Mac next month. This update will change the branding from Office 2016 to Office 2019 and it will also require macOS Sierra (10.12) as the minimum OS version.

It’s strange that Microsoft have picked this time to update the year in the software name. In January this year, Microsoft increased the major version number from 15.41 to 16.9, I wonder if the 2019 update will also bump the version number from 16.xx to 17.xx?

People on 10.11 or earlier will be unable to update to the latest version of Office for Mac, however they will continue to receive support and the older version of Office will continue to function.

Source: Upgrade your macOS to access new Office 365 for Mac features – Office Support