Check out the last paragraph of "Is WebAssembly only for C/C++ Programmers?" in the FAQ [0]. The tl;dr is that you'll be able to port a Python interpreter (that is itself written in C) to WebAssembly from day 1, but a more robust solution that relies on WebAssembly GC will have to wait until after the MVP.

[0]: https://github.com/WebAssembly/design/blob/master/FAQ.md#is-...