Unity 5.6 is now available as the final installment of the Unity 5 series. It comes with a Progressive Lightmapper preview, new Light Modes, Vulkan support and many more features.
Unity will be switching to yearly naming for future versions. If this is added to the splash screen, it will be a great way to force developers to keep updating their builds to ensure their games don't appear dated.
Source: https://blogs.unity3d.com/2017/03/31/5-6-is-now-available-and-completes-the-unity-5-cycle/