Ask HN: Web Development Language Post-PHP

Disclaimer: This is not meant as a pro-PHP/anti-PHP discussion, rather it is meant to be a discussion about what web development language will take over the world like PHP did in years past.

I've made an obscene amount of money with PHP over the past seven years or so, and I consider myself quite proficient. However, recently I've noticed that PHP is no longer considered the premier web development language. More and more, I've seen languages like Ruby, Javascript, and Python gain market share and popularity amongst my colleagues and the rest of the Internet.

Here's the question:

Should I continue to work with PHP, or should I consider learning another language to augment the decline of PHP over the next several years? If the latter, which language does HN feel will be the most relevant five years from now?