It's not really a new idea, though. IBM developed NetRexx, a version of Rexx which compiles down to Java, in the mid-90s, for example. Kawa, a version of Scheme for the JVM, dates back to 1996 or so.

I agree. It wasn't new, but back then it was an exception, something really different from the norm. Now it's a more common thing. Now it's taken for granted that different languages can target the same VM and interoparate without going down to C.

And JavaScript will be the most popular language, by far, for most types of applications.

Excel is a close contender. It's still the world's most popular programming language. It incorporates a zeroth order functional language (the spreadsheet).

Off-topic, but what's a zeroth order functional language? What are the other orders (something reqiring lambdas, closures, etc)? Google and Wikipedia didn't help.

This is a quote from a talk at the International Conference on Function Programming (or more specifically the Workshop for Commercial Users of Functional Programming http://cufp.galois.com/2009/abstracts.html). But Lee Benfield who said it, attributed the saying to Simon Peyton-Jones.

A higher-order functional language allows higher order functions like map, filter and foldl (functions on functions). A first order language allows to define functions, but not on other functions. And a zeroth order language does not allow you to define functions (or name anything) as far as I figure.

We're talking about the future, not the past. Excel, while astonishingly popular today, has nowhere to go but down.

It's a long way down.

Or will Javascript just be the machine language of the internet, with software written in more expressive languages such as Java via GWT?

Interesting thought. (Though I doubt that Java is more expressive than Javascript. I'd replace Java with something like F#, clojure, Arc, Haskell or so.)