Close to 370 million users world-wide may soon be on an unsupported version of Internet Explorer as IE 11 will be only version receiving updates after January 12, 2016 

http://www.networkworld.com/article/3010792/windows/nearly-370m-ie-users-have-just-6-weeks-to-upgrade.html

In August 2014, Microsoft took Internet Explorer (IE) users by surprise when it announced that most had to be running IE11 by Jan. 12.  After that date, Microsoft will support IE9 only on the barely used Windows Vista and Windows Server 2008, and IE10 only on Windows Server 2012. All others, including those with devices powered by Windows 7, Windows 8, Windows 8.1 and Windows 10, must run IE11 or Edge.

The retired browsers will continue working, but Microsoft will halt technical support and stop serving security updates for the banned versions.   According to data released by measurement vendor Net Applications, 44.8% of all IE users ran a soon-to-be-outdated edition of the browser.  That portion of the IE user base represented about 368 million users when Microsoft’s often-stated number of 1.5 billion Windows devices worldwide was used in the calculation.

More information can be found here:

https://blogs.msmvps.com/harrywaldron/2015/12/08/internet-explorer-migration-to-v11-required-in-early-2016/