Kotlin is taking off on the backend. It took a little longer than some people might have hoped but all the big boys are doing backend development in Kotlin now. Square/Netflix/Uber/Twitter/AirBnB all traditionally Java houses have adopted Kotlin in one way or another.

Scala on the other hand is facing a decline. Less so in Big Data where it is still doing well but I find increasingly it's not being chosen for new backend development.