JavaScript is going to get much bigger. My money is on that especially with node.js and html5 in the game. I also noticed F# was not even mentioned, purposefully or mistakenly?
I know it has all sorts of negative stereotypes, but the combination of JavaScript and PHP is the new Visual Basic - something that will let someone who isn't an expert quickly make a useful GUI application. And it won't go anywhere VB didn't go.
Given that it really only hit the public consciousness last November or so, that's more or less expected. What makes people so bullish is that the number of JS developers isn't going to decrease any time soon.
It is, however, a pretty awful shell scripting environment and I don't know who would prefer it to Ruby. I say this despite writing a build system for it this weekend to drop dependencies on Ruby and Java. Coffeescript improves things but it's still pretty raw.
Threads on the other hand, are the often the wrong optimisation -- processes are the right one.
Node's async structure is just taking the async model of the web one step further, into processing the same request asynchronously if you need to wait for something else.
You might be master of doing this logic right, but I've audited tens (perhaps hundreds) of systems, and all the synchronous ones got it wrong.
(Disclaimer: I've never worked with Node. But I've been writing async servers in C and Python since 1999).
As we all know C, C++, C# and Java are these big mainstream languages of today with “recent” additions Python, Ruby, Javascript and, especially in the Apple world, Objective-C.
I totally agree with you that Javascript is going to get much bigger but to me it is already big so it doesn't even need to contend against the other languages in my blog post ;).