Refactoring Wordpress will make it even faster. Look at the difference between Drupal and Wordpress. It's amazing Wordpress is still used for big sites while a ton of recourses could be saved. But great work on the PHP engine!
Agreed. I ran a benchmark against CodeIgniter on a test box recently and was suprised that a single query app performance went from around ~20k req/s with raw PHP (no framework) to around ~3k req/s with CI and thought that was bad for a framework. I didn't realize Wordpress performance was so much worse especially given its popularity. Most Wordpress sites use a caching plugin like WP Super Cache or Varnish-type setu…
In my own benchmarks i've noticed all that class loading and instantiation slows things way down, even with an opcache. I find that a namespaced procedural / functional architecture performs much better, but no PHP framework works that way.