Previewed at WWDC, launching in the fall.
Apple Seeds Second Beta of iOS 9.3.3 to Developers
The second iOS 9.3.3 beta can be downloaded from the Apple Developer Center or over-the-air with the proper configuration profile installed.
As a minor 9.x.x update, iOS 9.3.3 appears to focus on under-the-hood bug fixes and performance improvements to address issues discovered since the release of iOS 9.3.2. No outward-facing changes or obvious bug fixes were found in the first beta of iOS 9.3.3.
There was originally no iOS 9.3.3 update released for the 9.7-inch iPad Pro because Apple needed to fix an iOS 9.3.2 bug that bricked some devices, but it was addressed in a new iOS 9.3.2 update last week. iOS 9.3.3 is now available for the 9.7-inch iPad Pro.
We'll update this post with any changes that are found in the second iOS 9.3.3 beta.