I'm sorry to say that this is not an accurate portrayal of how PHP is to be developed in the future. There will be a new major version of PHP: so-called PHP 7 to avoid confusion with the defunct first attempt at a PHP 5 successor.[1] This new major version will contain a completely new engine[2] that is definitely not backwards-compatible with PHP 5 extensions (though it should be backwards-compatible with userland code). The new major version also opens the door for any userland-level breaking to the language; the first three of which are a change to integer semantics,[3] an AST,[4] and a uniform variable syntax.[5]
Instead, I'd characterize PHP 5.3-5.6 as more pragmatic than visionary: PHP 6's major backwards-incompatible feature was going to be full Unicode support, and when that didn't pan out, PHP 6 no longer had a raison d'être. Instead of holding onto a number of useful language features for a few more years until a new major backwards-incompatible change was developed (now the new parse engine), they backported them to PHP 5.
[1]: https://wiki.php.net/rfc/php6
[2]: https://wiki.php.net/rfc/phpng
[3]: https://wiki.php.net/rfc/integer_semantics