[steedsofwar]

This may provide some insight:

http://blog.jetbrains.com/kotlin/2011/08/why-jetbrains-needs...

The nice thing about that post is that they (Jetbrains) are pretty honest about the whole things e.g.

"First and foremost, it’s about our own productivity."

"The next thing is also fairly straightforward: we expect Kotlin to drive the sales of IntelliJ IDEA. "

"The final point is less obvious but still important: new programming languages is a topic that many people really enjoy talking about, and the first days that have passed since we’ve unveiled Kotlin prove that."

"And we’d like to reiterate that our work on Kotlin does not in any way affect our investment into other development tools, and in particular the Scala plugin. If you’re already happy with Scala and have no need for another new language, we’ll continue to do our best providing you with first-class Scala development tooling."