Great news. HHVM and now PHP 5.7, both with JIT - the future of PHP looks bright.
To my knowledge a JIT compiler is not being added to PHP 5.7. Can you clarify your comment or provide a link to the source where you heard this?
The linked email in turn links to the PHP NG page (https://wiki.php.net/phpng) on which the version number mentioned is 5.7.0-dev