From that article last year, Canonical's Stephen Webb had written, "[Vulkan 1.0 is] officially out. Full support in the Mir display server will be landing in time for inclusion in Ubuntu 16.04." But as we have covered in the months since, that never happened. Toward the end of 2016, we heard that Mir Vulkan support should be ironed out for Mir 1.0. We are expecting Mir 1.0 to be released in 2017, but beyond that there isn't any clear public communication when that release will be available, but hopefully by Ubuntu 17.10 -- especially if they are still planning for Unity 8 + Mir by default for Ubuntu 18.04 LTS.
It looks like Ubuntu Mir developers are working towards the Vulkan support and recently hitting their codebase were some Mir presentation chain changes and then a change explicitly for Vulkan with expanding Vulkan's presentation support on Mir.
The code doesn't appear to be all public yet for Vulkan support on Mir, but at least progress is being made, one year after Vulkan has been running on the X.Org Server and Wayland.
Another recent Mir change worth reporting is improving the concurrency of the IPC and compositor threads as a "first step" towards fixing GPU saturation issues with Mir. Bugs causing this work were Gallium3D EGL clients causing Mir to slow and Mir hitting 100% CPU usage.