Earlier quoted context omitted.
Actually Scala 2.12 will have more Java 8 Interop than Kotlin. Scala will hit soon while I don't see Kotlin Java7/Java8 soon not even a Milestone release yet.
Even Scala 2.11 has better Java 8 interop. The main change in 2.12 is that Scala itself uses Java 8 features like default methods and invokydynamic. Using Java 8 has worked with 2.11 for quite some time already.
and Scala 2.12 change FunctionN to FunctionalInterfaces. That will add a huge boost to Java8 Scala 2.12