Whenever the Eclipse platform is started it detects and notes any changes that have been made to the installed base of files such as the appearance (or disappearance) of feature and plug-in versions. New or updated features are not automatically configured for an existing workspace; rather, you are told on start up that there are updates and given the opportunity to configure them. If you accept them, the new and updated feature versions become a part of the feature and plug-in configuration used for that workspace. If not accepted, the new and updated feature versions remain dormant (disabled) for that workspace, but available to be picked up at a later time.
To pick up pending changes:
Updating Eclipse with the update manager
Restoring a saved configuration