Count on Apple announcing iOS 12 at WWDC 2018 in June. At this event we will learn about some of the biggest new iOS 12 features and what devices will get this upgrade.
Apple normally delivers an iOS beta that same day, allowing developers to start testing apps on the new release and if Apple sticks with the tradition a public iOS 12 beta release will likely come a few weeks later.
The iOS 12 update will likely include new emoji and may allow you to change the direction emoji face. Another rumor says that Apple plans to allow developers to make apps that work on the iPhone, iPad and Mac starting with iOS 12 and macOS 10.14.
Expect to see more iOS 12 leaks later this Spring as we draw closer to the event.