Preview at WWDC likely in June, followed by September launch.
Apple Seeds First Beta of iOS 9.3.2 to Developers With Bug Fixes and Improvements
The iOS 9.3.2 beta, build 13F51a, is available for download immediately from the Apple Developer Center and may be made available to public beta testers later this week.
We don't know what changes iOS 9.3.2 will bring to iOS 9, but according to its release notes, it focuses on under-the-hood performance improvements and fixes for bugs that have been discovered since the release of iOS 9.3. We will update this post with any changes that are found in the new beta.
What's new in iOS 9.3.2 beta 1:
Quick Actions - Quick Actions now open up smoothly in landscape mode with none of the jittering or lag that's been present in past versions of iOS 9.3.