Unity 5.5 was only marked as a stable release a couple of weeks ago, but that hasn’t stopped Unity from releasing the 5.6 beta today.
Unity says 5.6 will wrap up the Unity 5 cycle when it launches in March 2017. The final version will pack a number of improvements including a progressive lightmapper, a Mac Editor on Metal, and several new features designed to improve 2D game development workflow.
Support for Vulkan and Metal Compute will also be added, as will native support for Google Daydream, Cardboard, and Facebook Gameroom.
Check out the 5.6. release notes for a full list of features, improvements, and known issues.