PG explicitly states in the essay that it's not that much on Java itself but rather on the way hackers judge technologies (the "hacker radar" in his expression).
And these are not quite predictions but statements on how Java is (or was then back in 2001) perceived.
And I think, IMHO, a substantial part of the Java success today should be attributed to the JVM, not so much to Java, the language. Clojure/Scala/etc. are kind of clues for this.
It also helps that it's one of the languages being taught in CS classes.
I don't think so. Java as a platform is a lot easier to manage than most other platforms, including Ruby and Python. Jars, in my experience, are much easier to deal with than Gems. Java has a set of advantages that aren't really replicated elsewhere. It's garbage collected and portable, but executes much faster than other garbage collected and portable languages.
I feel pretty much all those reasons are specious and really shouldn't be holding things back. We've got a foothold established with success of some smaller projects using Groovy and Ruby to "prove" their viability. I'd like to try Scala next to see how it would fit for some of our other projects.
TLDR: At least one large company is making efforts to evolve beyond just Java in the JVM.