Charles Nutter has started an interesting Google Group which is worth the attention of language wonks: http://groups.google.com/group/jvm-languages
I recently spent a pleasant hour thinking about Common Lisp on the JVM; see this thread: http://groups.google.com/group/jvm-languages (Kicking off: Jatha)
Meanwhile, the JSR 292 Expert Group will be working this summer on a simplified POC (proof of concept) that can serve as the basis for coordinated experiments in JVM and language implementation.
I expect that when we have something that passes the red-face test, we will be soliciting comments and experiments, based on open source bases. This is not the Final Answer, but simply the Initial Answer.