And the MS Common Runtime is optimal for C#... and a few other (scripting) languages. With hacks, so you get Eiffel# and Perl# and Python#.
I agree with your point, that Sun should keep alternative languages in mind, but that isn't their design goal. They have one goal: Making Java run well on all platforms. Anything else is just gravy.
I also think we won't be seeing too much .NET code in anything beside C#. Or VB.NET. Call it a hunch.
BTW, I've used Jython (java + python), and it doesn't seem "hacked" to me. It's always performed quite well, and has a pretty seamless integration.