Sure Kotlin is cool but as Paul has stated, a lot of Java developers would just add it as part of their Arsenal. I have spoken to other Java developer, especially those who had already experienced the "shiny" Kotlin features on other languages such as Scala and the rest, they are not necessarily as excited about Kotlin as Android developers.
Kotlin's major market is Android and the issue with Android isn't Java, but that the developers are stuck with Java 7-ish features.
The companies using Java should focus on trying to use the latest Java features, it's very likely those companies are using Java 8 or even Java 7. They could upgrade to the LTS JDK 11 and use the latest features instead of migrating to a new language. I feel it's not a necessary action.
In the next five years, Java would still be kicking and kicking even harder, it's great to have additional Languages like Kotlin and Scala in the JVM, these languages have the luxury to try out features and see if it works, Java learns from their experiments, Java does not have that luxury because of the number of systems depending on it, the stewards of Java have to make sure a feature is needed before adding it... and a lot of very cool features are on their way.
I see the JVM languages as an awesome team rather than competitors.
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