As a followup to the original comment a few changes have occurred on the Kotlin side:

• Kotlin (since the 1.2 release) now has its own multi-platform system (ready for production use)
• Support for iOS development is available in Kotlin Native (experimental)
• There is a recent Python extension sample for Kotlin Native on GitHub (experimental)
• Kotlin Native has been ported to WASM (experimental)
• Gradle Kotlin DSL (used for writing Gradle build scripts in Kotlin) will have a stable release in Q1 2018
• Bruce Eckel (VERY famous technical book author) is writing a book on Kotlin called Atomic Kotlin
• There was a Kotlin Conference (KotlinConf) this year (150 talks) which sold out very quickly!; Here is the keynote
• Kotlin JS has a library to support developing React apps (via a DSL)
• A Kotlin ecosystem is forming for Data Science
• Netflix have a production level system on the server side written in Kotlin called Orca that processes around 8 billion messages daily (Google scale)