Google Adwords announced via a G+ post that they will be adding another extension to Adwords. The new extension, called Dynamic Callouts, will automatically generate callout extensions based on the most important information about your business. Google said this about the new feature:
Dynamic callouts are generated based on the information on your website, helping reduce the amount of time you spend managing individual callouts. However, it’s important to continue adding and optimizing callouts because dynamic callouts may not show for all advertisers. You can add your own callouts at the account, campaign, or ad group level. We’ll always prioritize showing the callouts you provide over dynamic callouts.
Google still suggests you build out your own callout extensions to ensure you have the most control over the extension.