You're directly or implicitly assuming that:

a) Java is a bad technology and it's not moving forward ("once companies move to a better technology")

b) new Java developers aren't being trained, including very young and bright ones, straight out of universities, and they don't enjoy Java

Both claims are false.

Exactly. Even-though my livelihood right now comes from Python, I was trained in Java in my university(along with C). I did some coding(web scrapping) in Python but that was it. I still can and willing to write in Java.