AppleInsider:

As detailed by Apple at a session during its Worldwide Developers Conference last week, games will have access to new tools for inviting friends to multiplayer games via the Messages app.

Apple told developers that those already using existing Game Center invitation APIs won’t need to make any code changes for iOS 10. Messages-based invites will automatically replace the old method of inviting friends to play, and anyone can be invited via the Messages app and iCloud.