Google has just announced that with the release of IE11, which is part of Windows 8.1, it will remove support of IE9, which was expected as Google have a policy of not supporting browsers other than the most current version and the previous version.
What is surprising is the speed of this given that IE11 has only been released for a few weeks, and especially considering that it isn’t even available for Windows 7 yet.
Update: IE11 has now been released for Windows 7

Warning message about using an out of date browser
When using Googleapps, such as Gmail, with IE9 the user will be presented with a warning message stating that the browser being used is out date and should be updated.

IE9 default browser within MD7 Managed Desktop
At present the University has IE9 installed within the Managed Desktop as the default browser due to some corporate applications not being compatible or supported with IE10.

The University did consider using IE10 for the current version of MD7 this year, but this was not done as it was considered that there was not enough assurance that it wouldn’t adversely affect our Corporate Applications or Teaching and Learning applications.

Future of IE9 within the University
We are actively considering our usage of IE9 within the University and have requested that is confirmed that all Corporate applications and Teaching & Learning applications will be supported if IE10 is installed, whilst considering solutions for the few applications we know are not supported.
At present the applications that are known to have issues with IE10 are just used by staff members.

For further info see:
Google drops Internet Explorer 9 support in Google Apps less than three weeks after IE11′s release