Apple has released the first public beta versions of both OS X 10.11.4 and iOS 9.3, two point release updates that include some notable new features. The beta releases are the same as the recently unveiled developer betas of the same OS versions, and can be downloaded now by users who are enrolled in the iOS and OS X public beta testing programs.
OS X 10.11.4 public beta 1 includes support for Live Photos in the Messages app, secured Notes, as well as compatibility with iOS 9.3.
iOS 9.3 public beta 1 includes support for password protected Notes app, a flux-like NightShift mode (related; you can side load a similar app onto prior iOS versions with Xcode called GammaThingy), support for multiple users in educational environments, and a variety of new 3D Touch shortcuts.
Any user can choose to enroll in the public beta testing programs, but be forewarned that beta system software is notoriously buggy and can lead to a less than desirable experience. Thus, running beta software is really only recommended for advanced users, or for secondary non-essential hardware.
Separately, a minor update to the developer release of iOS 9.3 beta is available versioned as “1.1”, presumably bringing it up to the same build number as iOS 9.3 public beta 1.
Apple typically goes through multiple beta versions of system software before releasing it to the general public, and there is no known public timeline for iOS 9.3 or OS X 10.11.4. Some speculation suggests that both final versions could arrive late next month or in early March, possibly alongside hardware updates.
iOS 9.2 and OS X 10.11.2 are the most recently available public versions of system software available for Apple hardware.