Unless you have a job offer that specifically requires you to use Node.js, it's not really a question of "switching" - it's more a question of adding Node.js to the list of frameworks you know.

As far as jobs go, outside of Silicon Valley it seems that there is still a huge market for PHP programmers, and those Drupal/Joomla/Magento/WordPress sites aren't going away any time soon.

I'd also recommend Python, which many PHP programmers instantly like. Getting started with Flask (http://flask.pocoo.org/) should be fairly easy. Several big sites like Instagram and Pinterest are powered by Python.