Extension Manager supports updatable extension. If your existing extension specifies update URL in its mxi file, when the new version of the extension is available, you can put the update information file to the URL. Extension Manager will detect the extension update during launch and notify users. After user clicks the "Update" button, the updated extension will be downloaded and installed.
Extension Manager also supports command line interface. You can put the extension to a shared loacation, and write a batch file using commands. Send the batch file to all customers to run.
More detailed information about updatable extension can be found in http://www.adobe.com/go/em_file_format .
About command line interface, please see http://help.adobe.com/en_US/extensionmanager/cs/using/WSB4845EDD-14E5-476a-B749-FF328830D1 4F.html .