Preview at WWDC likely in June, followed by September launch.
Apple Seeds Second iOS 9.3.2 Beta to Developers With Night Shift and Low Power Mode Update
The second iOS 9.3.2 beta is available for download over-the-air or from the Apple Developer Center.
Like iOS 9.3.1, iOS 9.3.2 is a minor update that appears to focus mainly on under-the-hood performance improvements and fixes for bugs that have been discovered since the release of iOS 9.3. According to Apple's release notes, the beta features "bug fixes and improvements," including a possible fix for a major Game Center bug that has plagued iOS users for months. No outward-facing changes were found in the first beta, but we'll update this post with anything new discovered in the second beta.
What's new in iOS 9.3.2 beta 2:
Night Shift and Low Power Mode - iOS 9.3.2 beta 2 brings the return of a much desired feature, re-enabling the ability to use Low Power Mode and Night Shift at the same time. Early iOS 9.3 betas allowed Night Shift and Low Power Mode to work simultaneously, but it was removed in iOS 9.3 beta 4. With iOS 9.3.2 beta 2, you can turn on Low Power Mode when Night Shift is on.