At least for the company I'm working now, and when you already use lombok, adopting Kotlin is a small step. Also it's easy to have both Java and Kotlin in the same codebase. But with records likely to be in Java 14, it doesn't seem that appealing to me. I would actually prefer Java over Kotlin, mainly because better ironed out best practices. The Kotlin code is often harder to read than the Java code. Still would prefer Clojure more, mainly because it's more functional.