Given that the RoboRIO is an embedded system, using an unsupported language of your own choosing on the RoboRIO should be relatively easy task, particularly compared to getting one working on the cRIO.
The part that is 'hardest' is creating sufficient bindings for WPILib. However, SWIG wrappers already exist that were created for the LUA interpreter (obviously would need to update them), and
SWIG can create bindings for a
*lot* of languages, including C#. Should be easy enough to get it working for other languages.