You don't have to work for wordpress.com, though. For example, I do some PHP coding for a media company, which also happens to use Wordpress - WP with redis cac

You don't have to work for wordpress.com, though. For example, I do some PHP coding for a media company, which also happens to use Wordpress - WP with redis caching can run a big site also. So yes, there is still php work floating around. Incidentally, their internal tools (content auditing, SEO, ...) is also being done in PHP...