If you are a perpetual license holder for Unity 5.x, then your last free update has just arrived. Unity 5.6 brings Vulkan for Windows, Linux, and Android. I just installed the new version and checked to see which graphics APIs it uses on Windows when you uncheck the auto box, and the list comprises of DirectX 11 and DirectX 9. It’s possible that auto could be choosing Vulkan, but I’m not going to query which process is loading which DLL under a variety of conditions. If you’re interested in Unity development, go to File -> Build Settings -> Player Settings -> Other Settings and choose the load order of your APIs, using the + button to add one that’s not there by default.
The lighting system should be more impressive, though. In Unreal Engine 4, I’m used to having dynamic lighting until I stop everything and start a lighting bake. When it’s done, I have static lighting until I invalidate it with a change (and the level is set to invalidate light maps on changes). In Unity 5.6’s case, though, it will just slowly replace the light maps as they are calculated, getting progressively higher quality. Since you can notice problems at low quality, you only need to wait as long as it’s required to see the errors, which speeds up development.
In terms of platforms, Unity 5.6 adds Daydream, Cardboard, Nintendo Switch, and WebAssembly.