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.)