Java will never "catch up" to Scala (for example, the type system / generics will not evolve in the foreseeable future).
But once Valhalla lands, with some additional JEPs, Java will be very close to the core of what Scala offers. Where there are gaps, some of these can be filled via libraries (think immutables.org, or others providing persistent data structures).
As a matter of fact, these days at most companies that I see the typical deployment model is "micro"services, which you can quickly develop via Spring Boot or the alternatives. No need for ultra complex code or asbtractions, Java does it just fine. And you have all the tooling you need for the enterprise world.
I think Scala is an excellent language for teaching ML-style programming. I would still recommend it for that purpose. But there is no longer a killer app or need for Scala, that would convince most people to use it for new projects.
Just like Scala by virtue of being a guest language on the JVM ecosystem, never will replace Java on the minds of JVM architects.
Kotlin has an advantage here, because ART nowadays is effectly KVM from Google's point of view, where they grudgingly update Java support to keep up with Maven central.
Scala has nothing like this, and the update on Python alongside native libraries, kind of stole its demand in big data, hence why this kind of scenarios is described on the article.
They're not in the same playground. Scala has a far more advanced type system - more close in power to Typescript or Rust than Java - and capabilities like compile time metaprogramming which aren't on the Java roadmap. Or more mundane things like immutable collections or a copy method for "record" classes.
Whether that's an advantage in day to day business development is a different question.
Yes, Java has been getting a lot of features Scala has had since (more or less) always. But it's a continuing process, and not all such features are yet fully fleshed out and polished in Java.
Also, Java will probably never get many of important features Scala has (or will have). It may not be some esoteric things, like higher-kinded types. But things like meta-programming/macros. Or features which may be advanced from theoretical point of view, but are actually easy from user point of view (because they lead to a simpler code), like Capture Catching.
If capabilities (Capture Catching) proves to be very useful (and really solves the problems it claims to be able to solve) then it's likely that Java will also implement it, no? So... in about 8-15 years?
I doubt it. For Capture Catching of Capabilities to work, you need some of the unique sauce practically only Scala has. E.g. Contextual functions or path-dependent types. Java almost certainly won't adopt these.
