Preview at WWDC likely in June, followed by September launch.
Apple Seeds Third iOS 8.2 Beta to Developers
The beta, Build 12D5452a, is available immediately to registered developers as an over-the-air update and it can also be downloaded from the iOS Developer Center. Today's update also includes Xcode 6.2 beta 3 with WatchKit.
According to the release notes, iOS 8 beta 3 fixes several bugs including an issue that caused opening Messages conversations to take a long time and a missing emoji button in iOS Simulator. It also includes two fixes for WKInterfaceController methods: openParentApplication:reply: now launches the containing app in the background when the iPhone (or iOS Simulator) is unlocked or locked and presentTextInputControllerWithSuggestions:completion: is now fully supported in iOS Simulator.
iOS 8.2 includes the WatchKit SDK, allowing developers to create apps, Glances, and notifications for Apple's upcoming wearable device ahead of its 2015 launch. The first iOS 8.2 beta, with WatchKit SDK and developer documentation, revealed several new details about the Apple Watch, including its heavy reliance on the iPhone and the different types of content developers can create for the device.
Update: It appears the latest beta reintroduces blood glucose tracking in the Health app and adds new descriptions for various Health app features.