"Beginning January 12, 2016, only the most current version of Internet Explorer available for a supported operating system will receive technical supports and security updates."
The latest Internet Explorer version that runs on Windows Vista is Internet Explorer 9. So there will still be users using that... Windows Vista will have security updates till 2020.
Chrome will drop support for Windows Vista and XP in April 2016. Firefox still supports Windows versions all the way back to XP SP2. About 14% of Firefox users still run XP!
"Beginning January 12, 2016, only the most current version of Internet Explorer available for a supported operating system will receive technical supports and security updates."
The latest Internet Explorer version that runs on Windows Vista is Internet Explorer 9. So there will still be users using that... Windows Vista will have security updates till 2020.