Kotlin is no-longer new. As of 7 May 2019, Kotlin has been the official “preferred” language for Android development according to Google.

Google has been using Kotlin for Android apps since 2017 and the pair have jointly supported the Kotlin language through the Kotlin Foundation since 2018. In 2019, Google's Android team adopted ...

It’s no surprise that Google’s hope is that over time, all Android developers will switch over to Kotlin. “There is still quite a bit of Java still happening on Android,” Ward said.