Microsoft's Crissy House published on the Windows Server Division WebLog that there will be no SP3 release for Windows Server 2003

We have received inquiries from our customers and partners on whether or not there will be a need for a Service Pack 3 for Windows Server 2003. Microsoft will not have a SP3 release for Windows Server 2003.

To Summarize...

Self-Help Online Support* will be available for Windows 2000 Server after Extended Support before it ends on July 13, 2010.
Windows Server 2003 and Windows Server 2003 R2 will begin an extended support phase on July 13, 2010
There will be no Service Pack 3 for Windows Server 2003
*Self-Help Online Support is available throughout a product's lifecycle and for a minimum of 12 months after the product reaches the end of its support. Microsoft online Knowledge Base articles, FAQs, troubleshooting tools, and other resources, are provided to help customers resolve common issues.

>> Support changes coming July 2010 for Windows Server 2003