I see a couple of issues with the Mac / TF OpenCL situation.

Apple is pushing metal and performance shaders, I would not bet on strong support from them keeping up to date drivers with performant ocl. I asked at wwdc17 about vulkan and they clearly do not want it on their platform.

The TF OpenCL issue is vocal on the repo. Yet to see progress for macos. https://github.com/tensorflow/tensorflow/issues/22

Last but not least there is an issue with the ocl support. It is (was?) done on linux using computeCPP, compiled to SPIR (Standard Portable Intermediate Representation). MacOS does not support SPIR at the moment.

My best guess would be to use IOMMU magic and hardware virtualization to hook a GPU to a linux VM with MacOS as a host.