Kotlin looks(ed) promising. When I tried Kotlin some time ago they mixed plans, wishes and facts in the "documentation" which made it very hard to do some work, as many "features" in "examples" had not been implemented (And I thought to myself how stupid could I be to not get the examples working)
Yes the official documentation is indeed out of date. I am working to fill the gap (http://goo.gl/TkgqR - in progress)
The potential growth for Kotlin usage will be on Android platform especially after the new Android Studio is based on IntelliJ 13. Kotlin fits nicely here and it's a relatively small language.
Scala though is quite a pioneering language on the JVM. I think a lot of Kotlin features and design are influenced by Scala.
