Stephen Colebourne gave an entertaining talk to a packed room called The Next Big JVM Language. He went over the features of such new JVM languages as Groovy, Clojure, Scala and Fantom (which I’d never heard of).
He seemed to be leaning toward Fantom as the language of choice before delivering the punchline that the best candidate for the Next Big Language might be a backwards incompatible version of Java itself.
I think I agree. Oracle should get rid of all that legacy crap in JDK 9.