If you think Android is 90% of the market and considering Kotlin is seeping rapidly into Android, this is a great time to do it. It's interchangeable with most of Java.
Kotlin offers much of what Swift does, both try to adopt the same features as the other. It does pseudo-functional programming nicely, which is what a lot of people look for these days.
If you want to compare career paths for both, Dart/Flutter is still early and doesn't have enough data points. Kotlin's popularity grew at a similar rate early on, despite no MFAANG backing, and now Google is officially replacing their docs with it. The fact that Google pumps out so much recent effort into building up both native Android/Kotlin and Flutter/Dart means something, but on a gut feel they're investing more into Android/Kotlin/Jetpack.