One of the first things that most people do when they get a new Android device is to log into their Google account. That allows the preinstalled apps to update automatically, among other things. Updates are important because often the update is meant to patch some sort of flaw that makes the app or device unstable or to patch a security hole that leaves devices vulnerable. The problem is that not everyone logs into a Google account on their device.
That means apps are left unpatched and Google wants to change that. Google is sending out messages to developers who preload apps on devices letting the devs know that it would be testing a feature that allows the apps to update even if the user fails to log into a Google account. There is no specific date for the feature to be trialed, all Google says in the message is that it will arrive "in the coming months."
Devs are warned that the user can turn the feature off if they don't want apps updated automatically. The warning to developers and the pause between announcing this feature and rolling it out is to allow the developers time they need to ensure that the updates they are rolling out work as intended for users who aren't signed into a Google account.
Google reckons that the change will make it less expensive for developers to support out-of-date versions of apps that aren't being updated. Another caveat to the new feature is that it will only apply to devices that shipped with Android Lollipop or newer versions of Android installed. Any of the devices before that version of the OS will still languish with outdated apps unless the user logs in.