Oh, absolutely! And don't get me wrong, I think Kotlin was the right thing to do ten years ago -- Java was not in a great shape back then (in fact, Sun drastically cut investment in the core platform) -- and maybe even five years ago. I also think it was very well designed -- very much in the "Java spirit" -- although I think it's taken things a bit too far recently for my taste.
> Imho it's coroutine system is the best in industry right now.
I think that coroutines for a platform that's already designed around multi-threading are a bad idea altogether (this goes for C# as well) unless the language has some very specific constraints, like C++/Rust. Some might disagree, but I don't think those would be people who've had experience with Erlang or Go (although those platforms, like all platforms -- including Java, of course -- have their own problems). Nevertheless, for quite a few it's certainly better than nothing.
> I would not be suprised if Kotlins designers already have decent plans on "what do we do if Java integrates Valhalla/Loom/etc"?
I'm sure they do, and I'm sure their solutions would be great, but they'll need to sacrifice some of their goals. In any event, it is no longer the "there's nothing to lose" proposition it used to be.
> And I think it's pure existence pushes the standards, and has a positive impact on the design of Java and other languages.
Maybe, although Java (the language) has so far taken little if anything from Kotlin (most of the inspiration to recent work has come from ML, and even Scala to some degree). If there is one Kotlin feature that I think might ultimately make its way to the Java language it would probably be nullability types; I think that that's its most impactful contribution to the design of other languages, too. What mostly pushed Java forward in recent years is the increased investment by Oracle, and competition from other platforms. If I were to pick a positive impact Kotlin has already had on the Java language, it is perhaps demonstrating that there is appetite among programmers in more conservative languages (as opposed to Scala and Haskell programmers) for new language features beyond lambdas.