If java was brainf&%k and we still got the JVM out of it, it would all be worth it. And I think there's a good chance that Java's successor runs on it.
Totally agree that the JVM is super powerful. I think it's Java's greatest strength. However, I don't see any current JVM language as a potential replacement. Scala is too complex. Clojure, while wonderful, is Lisp and no one has been able to make that popular for 5 decades (not even pg).
I'm looking a lot at Kotlin. It's not mature yet: JetBrains will start using it this summer for their own projects and I expect it to firm up a lot then.
The nice thing about Kotlin is almost perfect compatibility with Java, and an auto-translator that doesn't suck. So you can take an existing Java codebase and auto translate class by class, maintaining compilability the whole time. Also the standard library is mostly a set of extensions to the JDK so your existing library knowledge ports across, except you keep finding useful goodies sprinkled all over the place.
Feature-wise Kotlin has things that I feel would help me write fewer bugs: it has null-safety encoded into the type system, smart casts, extension methods, some good functional programming support, powerful properties and so on. There are features it lacks too, but I hope JetBrains will continue to push it forward for many years.
Groovy doesn't have much significant use anymore. Someone's gaming the stats to make it look more popular, though. At https://bintray.com/groovy/maven/groovy/view/statistics you'll see 190k downloads in the last 30 days, click on country and you'll see 162k of them from a proxy server in China, and only 8300 direct from the US.