Google Play Games is a backbone for just about any game you can download and install from the Play Store, requesting that players sign into the game upon opening it by way of their Google + accounts. The way things currently work though is that players have to sign in every single time they open the game as opposed to just the first time they play it. This year Google is changing things up and has announced a new Games API model for 2016 in an attempt to reduce the friction for sign-ins, as well as the number of permissions requests which Google feels are unnecessary.
With this new API model for Play Games, perhaps one of the biggest changes is that the players will no longer have to sign into their accounts every single time they open a game, but instead, will only be required to sign in once per account. This should help players spend less time signing into Google Play Games services and more time getting to the games they're trying to play. In addition, Google+ will no longer need to be a part of the Google Play Games account process, so new play games users won't need to "upgrade their account to Google+" to use the play games services.
As players will need to sign into games only once, future game sign-ins will be automatic and handled by the Play Games services, however, Google does state that the auto-sign-in can be disabled by users if they decide they don't want it. Accessing this particular toggle will require players to open up the Play Games app, then navigate to settings where they can find the option to turn it off. Existing Play Games users will continue to see their Google+ player ID upon sign-in while new users will get a brand new player ID that is different from the ones that are currently being used. While these changes should reduce the friction for the sing-in process and get rid of unnecessary permissions requests, Google notes that there could be some potential issues with things for developers, and have listed out a number of possible solutions should these problems arise.