I think his argument applies to most languages that are more powerful than what you see in the mainstream. You have to be in the 95 percentile of programmers to be able to use Common Lisp or Clojure correctly, or even to use some of C#'s newer and more advanced language features. In fact, for languages even more steeped in the academic world, like Racket or Haskell, I would pin that percentile more at 99.9.

Languages like Gosu and Kotlin are simpler, but just aren't bold enough to make a big difference in overall productivity. My personal hope is that some future generation of programmers is just better educated. I don't know how else any of these languages or tools will ever gain widespread acceptance.