As per the upstream vendors errata support policy, updates for CentOS 2 will also end on May 31, 2009.

It is recommended that any system still running CentOS 2 should be upgraded to a more recent version of CentOS before this date to ensure continued security and bug fix support.

More details are available from the RedHat web site at https://rhn.redhat.com/errata/rh21as-errata.html