We knew it was coming. Google was a partner of Vulkan since it launched, but support was coming at some point after the desktop launch. We expected that it would be soon, but now we know that the new graphics API is in Android N Developer Preview 2. Other platforms, like apparently the Samsung Galaxy S7, are able to ship Vulkan drivers, but it is “a part of the platform” in this Android N pre-release.
Vulkan is particularly useful for mobile because those devices tend to have many cores, but relatively slow cores, which drive a decently fast GPU. Whether the benefits end up being higher performance or just better battery life (as the CPU can downclock more and more often) depends on the application, but it can be useful for 3D applications, and eventually even 2D ones, like future Qt applications with many elements, or even web browsers (when drawing complex sites).
It's good that Google is supporting Vulkan, especially after their ban of OpenCL drivers from Nexus devices. We want a single GPU compute interface across as many platforms as possible. While Vulkan isn't as complete as OpenCL, lacking some features such as unified memory, it should be more useful than OpenGL ES compute shaders.