I just compare Scala's growth to that of Java or even Ruby (since RoR). I also think that this adoption is not the result of Scala's power features but in spite of them (really, there was little choice in the statically-typed JVM languages). But I really have no skin in this game, and Java does need a modern replacement to fill a certain niche, and I have a hunch it will be Kotlin.
Is this a theoretical thought or a practical consideration?
I think the Java ecosystem needs a good, mature language now ... and I fear Kotlin is still at least half a decade away from being stable. While Kotlin compares nicely to Java 7, we need to keep in mind that both Java and Scala won't stop being developed. So pragmatically speaking, it will need to compete against Java 12 and Scala 2.16.
