From the article:
It might take a few more years before all of the existing SQL Server 2000 applications are upgraded to newer versions of SQL Server.
SQL 2000 SP4 drops out of the extended support phase in April 2013. After that MS won't be doing any security patches, so security holes won't get fixed and your enterprise is at risk. So you need to be planning on upgrading within the next 36 months. http://support.microsoft.com/lifecycle/?p1=2852