To me it means in the first place that we can add a canned answer to the bugtracker which would say "PHP4 is not supported anymore, install PHP5" and close all PHP4 only reports.So no bug-fixes, no releases except for ones fixing critical security problems. And even that should be ceased either in say.. 1 or 2 years.
Also I would suggest removing links to PHP4 downloads away from the front page on the php.net site and maybe put them onto the museum site? Regards Marco