In order to make a comeback, Java first needs to fall from the TOP 3 languages used by professional programmers in the world.
https://insights.stackoverflow.com/survey/2020#most-popular-...
Java is currently losing Android devs to Kotlin. That could cause a precipitous drop in direct usage in the coming years.
A Java developer will pick up Kotlin much faster than, say, a Postgres developer will pick up Mongo. It takes a lot longer for a Java programmer to learn the Android environment than the Kotlin language.
If there were a trend from Java towards Rust or Go or Python, that would be a significant change in the world. If Java were to vanish tomorrow and everybody had to pick up Kotlin, the world would be pretty much the same in a week. Kotlin is nice, benefitting from a clean-sheet implementation of lessons that Java takes on only with difficulty, but it's not a wholesale break.
P.S.: Also I say Java, but I mean JVM, I club all JVM languages together, since that's more what I care about, is the strength of the Java ecosystem.
Caution doesn't make money, it just prevents losing as much money. When it comes to technology if you're waiting for everyone else to validate an idea, you're too late.
AWS loves Rust in the same way than Facebook loved PHP.
That doesn't mean much because it is true for probably most serious technologies out there. Most of those organizations also have a perl script somewhere. Does that mean their core products are written in perl? Nope.
That being said, Rust is certainly successful and seeing growing adoption.
