This reminds me a lot of posts I used to see on Javablogs 5-6 years ago. Not sure what that means, but I don't think it's the language so much as where people _are_ with the language. In 2005-2006, there were a lot of folks who'd spent almost a decade with Java. They were good at it, but they were also getting bored and looking for new horizons, and Ruby and Python were available. Beta versions of .Net rolled out in 2000, so we might have the same kind of phenomenon.
None of which is to say other languages might not be better. But being better has never been enough, on its own. If it were, C++ might never have gotten a start. Language popularity depends a lot on history. But boredom/dissatisfaction with a dominant language can help give a new language a chance.
I think a big part of it is also the dead weight that accumulates with older technologies. Sometimes it is a person just making a decision for the stability of their household or because they've been at it so long it is all they know. Whatever the cause, as a technology (particularly a language) ages, more and more people that are change adverse remain and those (many times the best and brightest) move on. Not really surprising, but a bit unfortunate for those who remain.
None of which is to say other languages might not be better. But being better has never been enough, on its own. If it were, C++ might never have gotten a start. Language popularity depends a lot on history. But boredom/dissatisfaction with a dominant language can help give a new language a chance.