In addition to iOS 9.3.3, Apple on Monday also issued first betas for OS X 10.11.6 and tvOS 9.2.2 to developers. The new 10.11.6 beta, build 15G7a, can be downloaded through the Apple Developer Center or via the Software Update mechanism in the Mac App Store, and tvOS 9.2.2 can be installed via iTunes or Apple Configurator.
Here are the release notes for OS X 10.11.6:
The OS X El Capitan 10.11.6 update improves the stability, compatibility, and security of your Mac.
And tvOS 9.2.2:
tvOS 9.2.2 contains bug fixes and security improvements.
In addition, a profile on the developer portal is available to update Apple TV to tvOS 9.2.2 beta. More details are available under Installation Instructions.
Please test your apps with this beta and file bug reports as needed.
Like iOS 9.3.3, these updates are going to be fairly minor, and likely released to the public in short order. WWDC is just around the corner, and Apple is expected to use its keynote at the event to introduce new versions of each of its platforms, including iOS 10, OS X 11, and the next major iterations of tvOS and watchOS.