Javascript frameworks change on an annual basis if not faster.
This is a trendy sentiment that is oft repeated but of dubious veracity. Seems to me that Angular and React have remained as the preeminent Javascript frameworks for quite a few years without much signs of a shakeup, with the exception of vue.js taking on some modest gains in popularity, but still decidedly in the shadow of Angular and React.
To be honest, I would've said going deep on JavaScript right now (React, React Native, etc) would give you a shelf life of at least five years.
Kotlin seems like a bit of a random recommendation - it's not in the TIOBE top 50, and a quick search for Kotlin jobs on indeed.com (the first job search site I found from Google) reveals several orders of magnitude fewer jobs than for anything mainstream (hell, even Haskell beats it comprehensively). Perhaps it's the next big thing though!