PHP 7 will be soon available and the benchmarks are promising!
The official benchmarks are impressive: most real world applications running on PHP 5.6 will run at least twice as fast on PHP 7. For detailed performance benchmarks, have a look at Rasmus Lerdorf’s presentation at PHP Australia.
Maybe thanks to PHP 7 Wordpress is finally fast. ;)
PHP 7.0.0 comes with new version of the Zend Engine with features such as (incomplete list):
Alone the speed improvement is just so exciting that we will be ready when PHP 7 is ready!