Let's start with 2000. Windows 2000 Server will reach the end of its extended support phase on July 13, 2010. This means that Windows 2000 Server will no longer be publicly supported, and you'll have to resort to 'Self-Help Online Support' for your support needs.
Windows Server 2003 and Windows Server 2003 R2 (at a supported service pack level) will move from the Mainstream Support phase to the Extended Support phase on July 13 2010. In this phase, Microsoft will continue to provide security updates and paid support, customers will still have access to security updates and Self-Help Online Support options; however, non-security hotfixes developed during the Extended Support phase will be provided to customers who enroll in Extended Hotfix Support only.
When it comes to a possible third service pack for Windows Server 2003, Microsoft is quite clear. "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 writes, "Microsoft will not have a SP3 release for Windows Server 2003."
If you manage Windows servers, be sure to take these changes into account.