Hi Hugh,
Due to some spam issues in the past, the Numba-users list requires a moderator to approve posts from people who are not subscribed. Since that's just Siu and I, there can sometimes be a half-day lag in approving posts. I'll delete the post stuck in moderation.
We don't have any current plans to support OpenCL and SPIR-V. We did some early work with OpenCL and SPIR had had major problems with both the limitations of the standard and also platform bugs with various vendor's implementations of the SPIR compiler.
That said, we have been in contact with a developer who now has a proof of concept for an OpenCL/SPIR-V Numba backend who should be posting it to their repo in the next few weeks. I've asked them to announce it on the list when that happens, as I know there are many interested people.