From the Google Apps blog:
Beginning November 22, 2011, we will end support for the Gmail App for Blackberry (installed native app). Over this past year, we’ve focused efforts on building a great Gmail experience in the mobile browser and will continue investing in this area.
Users may continue to use the app, if installed, however it will not be supported by Google, or available for download starting November 22. BlackBerry users can continue to access Gmail through the mobile web app at http://www.gmail.com in their BlackBerry web browser.