Google was looking for beta testers to sign non-disclosure agreements, if they wanted to participate in the beta of this update. This has been a secret project from Google. Google is working on a new webmaster feature around rel-alternate-hreflang which is the attribute to communicate to Google if there are alternative language based web pages for the specific web page the attribute is placed on. It can be confusing for bigger sites to use this, or even small ones. Therefore, Google is working up new ideas on this feature implementation.
John Mueller of Google said they are "working on something neat" around rel-alternate-hreflang and want some beta testers. In case you want to try it, you need to sign an NDA and be willing to test it on your site. Find below the post by Mueller.
Below is a screenshot of the webmaster update :