We could certainly deprecate it. I don't think we can make it go away completely, other than in the sense of "Returns VK_NULL_HANDLE when VKD3D_API_VERSION_1_8 or higher is specified.", or something along those lines.
That still means that a client compiled with vkd3d 1.7 and running with vkd3d 1.8 would receive a valid handle, right? So even in vkd3d 1.8 we still have to support a code path without the CS thread. It requires some more code, but it should be doable.