Apple has issued the second beta versions of iOS 9.3, OS X 10.11.4, tvOS 9.2 beta 2, and WatchOS 2.2 to users participating in the developer release testing programs for iPhone, IPad, iPod touch, Mac OS X, Apple TV, and Apple Watch. The new builds continue to improve features and enhancements on the respective operating systems, and include multiple bug fixes.
Developer builds for OS X 10.11.4 beta 2, iOS 9.3 beta 2, and WatchOS 2.2 beta 2 are available for download now from the respect Apple Developer center websites, and can be downloaded from the Software Update mechanism within iOS and App Store of OS X. Public Beta versions of OS X 10.11.4 beta 2 and iOS 9.3 beta 2 are also available through the App Store in Mac OS X and the Software Update function within iOS Settings.
iOS 9.3 will include several new features, including Night Shift mode which reduces blue light in the evening hours a la Flux for Mac and PC, password protected Notes, and multi-user logins support for educational environments.
OS X 10.11.4 includes support for Live Photos throughout OS X and within Messages app, as well as support for syncing to iOS 9.3 devices.
WatchOS 2.2 appears to mostly be a bug fix release, but some improvements to the Maps app are included in that beta build.
tvOS 9.2 will include support for Bluetooth keyboards, but also aims to fix bugs and offer various improvements to different Apple TV features.
Separately, Apple also released a final build of tvOS 9.1.1 for the 4th generation Apple TV.
There is no known public timeline for iOS 9.3 and OS X 10.11.4 final versions to be made available to the general public, but typically Apple goes through several beta builds before a final version is unveiled. There is some speculation that iOS 9.3 will arrive alongside revised iPad hardware, however.
Currently, iOS 9.2.1 remains the most recent stable version of iOS available for iPhone and iPad devices, and OS X 10.11.3 remains the most recent stable build of OS X software for Macs.