No plans to support untrusted languages as yet. Too many foot-guns built into that. You couldn't even believe some of the evil, insane things that we've done with that.
Trusted languages are far more likely. This one looks really, really cool: http://code.google.com/p/plv8js/wiki/PLV8
I guess I'm probably one of like three users of PL/python, especially since it's untrusted. Worth a check, though!