As previously announced, starting on September 23, 2013, call, app and sitelink extensions will automatically upgrade to their new formats. If you haven’t done so already, we encourage you to upgrade your extensions ahead of the September 23 deadline so you can take early advantage of the new features, accrue statistics on the upgraded extensions sooner, and ensure that your extensions continue to show.

Starting on the upgrade date, the following changes will take place:
The use of CampaignAdExtensionService.get for legacy call, app and sitelink extensions, will be available through October 23. You can use it to consult and compare your legacy extensions data with their upgraded counterparts.

If you allow your legacy extensions be auto-upgraded, the system will do its best to detect and avoid creating duplicate extensions. We recommend that you check all your extensions after the upgrade is finished to ensure they’re configured as you’d like.

To learn more about managing upgraded extensions with the AdWords API, make sure to consult the Feed Services guide. For a code example on how to upgrade extensions on your own, look in the migration folder in all client libraries.

If you have questions or need help with the upgrade, please visit us on the developer forum or the G+ page.

 - , AdWords API Team