Google's general intent with Google Play Games is simple. Google wants to provide a solid backend with common game features to developers who want to make more compelling games. Once developers integrate these features, Google's user base offers a cohesive score/competition experience.
Providing features like leaderboards and achievements, Google has managed to catch the interest of many game developers already, but we have reason to believe that Google will be peppering a few new features into Google Play Games some time soon, with an update to Google Play Services and the Google Play Games app.
Quests & Level Up Notifications
First, quests. Quests are major elements of some games, and - when handled properly - have the potential to create a really great game experience. The information available to us indicates that Google is planning on helping game developers add more compelling quest interactions into their games by keeping users aware of what quests are available and when.
Using the new functionality, Google Play Games would tell a user if a given game has any quests, and then (if the user opts in to notifications), notify the user of an upcoming quest, give them the chance to accept or pass on it, and then serve up reminders about when the quest starts and ends, along with a friendly notification once the quest is complete.
Similarly, we have reason to believe that Play Games will be able to tell users when they've leveled up in a game, using the existing Play Games toast notification style.
Our information also indicates that a feature called Snapshots will be making its way into games. Exactly how it will be implemented is not 100% clear yet, but there are a couple of possible options. It's clear that Snapshots will constitute an effort by Google to make saving in a game easier, so the functionality could introduce easier checkpoints, instantaneous saving, or easier cloud saving (the latter being a feature largely ignored by developers so far).
Google Play Games is a service that only works if developers are interested. When developers are interested, they'll implement these features in their games, and users will benefit by getting a great experience. Play Games has been picking up steam, but hopefully these new features will convince even more developers to hop on board.