The RFC (https://wiki.php.net/rfc/shortsyntaxforarrays) was actually rejected by the developers, I think it's only really been put in to appease large userland pressure. Find it rather amusing that a 2 change to the parser for an alias would be rejected on 'maintainability' grounds.
The voting results on the RFC page is from 2008 when it was rejected. The recent vote that decided its inclusion was here: https://wiki.php.net/todo/php54/vote. I think it had pretty solid support from core developers as well as userland people this time around.
The RFC (https://wiki.php.net/rfc/shortsyntaxforarrays) was actually rejected by the developers, I think it's only really been put in to appease large userland pressure. Find it rather amusing that a 2 change to the parser for an alias would be rejected on 'maintainability' grounds.