It is 08/08/08 today. The day they took PHP4 behind the barn and shot it through the head. The date of the official discontinuation of PHP4 — even for security issues.
Drupal's success depends on that of PHP, and PHP5's slow adoption rate has certainly been annoying. Hopefully, we can all move forward together now. Drupal is ready for it.
If you still haven't upgraded to PHP5, today would be a good day.