Plug-ins will (at least for the foreseeable future) take the form of writing custom nodes in Rust. That code will automatically compile to CPU and GPU (unless it requires an allocator or other things not possible on a GPU architecture). In the future that will extend to custom viewport tools, custom panels, etc. either through a traditional plug-in API or maybe even through defining all that in the node graph itself, since the graph is basically its own programming language.

We will probably also need to have bindings into a Python API since Python is so popular among technical artists. Precisely how that will be done is yet to be determined, since we have a lot to do before reaching that point.