I like the idea of opt-in typing for PHP via Hack which you can enter by beginning your PHP code with <?hh — Facebook have essentially taken everything that is wrong with PHP, every complaint that someone has ever published in a blog post or bug report, forum or IRC channel and built it into an improvement of the language.
PHP isn't going anywhere. It might be one of the oldest web languages, but I think the PHP space is starting to get better with Facebook's contributions to the language, Laravel 4 being a solid PHP framework and we can't forget that most Yahoo! products are built using PHP as well (even the recently acquired Tumblr is coded in PHP). Flickr! is probably one of their biggest PHP applications.
Event hough Facebook appear to have resolved the many complaints and problems of PHP, I am sure people will still find a way to complain about the language that powers most of the web...