Preview at WWDC likely in June, followed by September launch.
Apple Seeds Second WatchOS 2.2 Beta to Developers
The second watchOS 2.2 beta can be downloaded through the dedicated Apple Watch app on an iPhone running the iOS 9.3 beta by going to General --> Software update. To install the update, the Apple Watch must have 50 percent battery, it must be placed on the Apple Watch charger, and it must be in range of the iPhone.
watchOS 2.2, along with iOS 9.3, introduces support for pairing multiple Apple Watches with a single iPhone. Both updates are required, with each watch running watchOS 2.2 and each iPhone running iOS 9.3.
There are were no other obvious outward-facing changes introduced in the first watchOS 2.2 beta aside from an update to the Maps app, but the update undoubtedly includes under-the-hood performance updates and bug fixes to address issues that have been discovered since the release of watchOS 2.1.