> both of these languages are intended replacements for an 'old' language (Objective-C => Swift, Java => Kotlin)

It may be true for Swift but Google never claimed Kotlin is replacement of Java. I guess people are getting overly excited and making claims that Google did not. Kotlin is low effort developer friendly move by Google. Jetbrains will do work on language and tooling and Google would provide some Android-Kotlin related docs and support.