With GPU support and eventually GUI support incoming, I think WSL has basically hit maturity for me. Any other features past here are "nice-to-have" but not a must. Between WSL 2, the new terminal, VSCode remote, the new Docker backend, a package manager, and everything else, it's really starting to feel like there's a unified vision now for Windows as a developer platform. Personally I'm really looking forward to what the future brings.
The killer upcoming features:
* Wayland support for running native GUI apps. X410 is pretty good, but it has all the limitations of a remote X server.