In a new post to his blog today, Brandon Savage talks about the "fade time" for PHP4 and how, really, it's gone on long enough.
Sadly, developing for PHP 4 backwards compatibility is something that companies and individuals are still doing. Wordpress released a new Widget API in version 2.8 that relies on the old-style PHP 4 constructor. Apparently, for Wordpress and many other developers, wide adoption is more important than language improvements.
This all came about because he noticed the Log PEAR package still supported PHP4. He's been making updates, though, to bring it out of the shadows and into the light of PHP5-only support.
Still, I look forward to the day when PHP 4 finally does go away forever, leaving us with a much better code base and happier developers.