IMHO, I'm not sure if any of the above there besides the testing libraries is something that should be part of Kotlin, _especially_ if it hasn't even yet hit v1

IMHO, I'm not sure if any of the above there besides the testing libraries is something that should be part of Kotlin, _especially_ if it hasn't even yet hit v1.0. That having been said, I think your concerns will be addressed, _eventually_, but JetBrain is not trying to disrupt Java or its ecosystem before mainstream adoption of the language. Re: async capabilities like Erlang/Go, until the JVM can support continuations, an industry standard solution like bytecode instrumentation, which Java9 will improve on, will entrench libraries like Quasar / RxKotlin to be basically drop in. These libraries provide seamless interoperability with existing synchronous libraries (see https://github.com/puniverse/comsat https://github.com/puniverse/comsat) to get around the fact that Erlang's/Go's async capabilities are not built-in to the language.