I really don't foresee any of these alternative JVM languages getting much traction in my industry (Defense/Aerospace).

I use Scala where I can at work (mostly smaller projects where I am the only developer and can thus get away with it), but every place I've worked over the last few years has been staffed with developers who are actively hostile to the thought of using any language other than Java. And right now, Java is king in the Defense industry. It's the new Ada, except I'd rather be coding in Ada than Java.

On my own side projects, I don't use Scala, because I would never choose to target the JVM for greenfield development. But that's just me.