https://support.microsoft.com/en-us/lifecycle?p1=15627&wa=wsignin1.0

Microsoft has significantly extended support for Office software, "Office for Mac 2011".
Originally, the company wanted to deploy updates for Office 2011 only until January 2016.
Now the support period was extended by one and a half years.

According to Microsoft, Software Updates will still be released until October 2017.

Thereafter you can continue to use Office 2011 without restriction,
but no Security Updates to eliminate Errors and Vulnerabilities will be released,
which can be a security risk in companies that use the software.

With “Office for Mac 2016” Microsoft made this month (07/2015) the successor of Office 2011 available.

Currently, Office 2016 can only be rented via a Subscription of Office 365,
a paid version will follow, according to Microsoft, in September 2015.

Office 2016 provides a revised Version which is getting closer to the Windows version with its user interface & it got optimized for the latest Mac operating system.

Word, Excel and PowerPoint have been converted to the Cocoa framework and support the 64-bit mode (Outlook is for some time offering already 64-bit support),
multi-touch gestures and high-resolution retina displays. And there are also numerous other innovations.