Microsoft Office for Mac 2011 was released over six years ago, and it's about time for Microsoft to lay it to rest. Indeed, Microsoft has announced that Office for Mac 2011 will reach the end of support in October of this year and that it won't be supported on Apple's upcoming operating system, macOS High Sierra.
The announcement was made on this support page, which explains that Word, Excel, PowerPoint, Outlook and Lync have not been tested on macOS 10.13 High Sierra, and no formal support will be provided after October 10th, 2017. It is also pointed out that after this date there will be no new security updates, non-security updates, or free or paid assisted support options or technical content updates.
Once this date it reached, Office for Mac 2011 will no longer be an option for download through the Office 365 portal. Microsoft is urging users to prepare for the upcoming change by installing Office 2016 for Mac to "have the latest and greatest features and support." This can be done by going to Settings, Office 365 settings, and Software in the Office 365 portal.