The company published a beta of SP1 last week in the hope that users will contribute towards ironing out any bugs prior to a public release, but did not disclose when the final release will occur.
Microsoft has now confirmed that this could be almost a year away, suggesting that the firm is comfortable with the current security state of the two operating systems.
Windows 7 went through a similar 'advanced users' beta test, which allowed Microsoft to build an impressive head of steam prior to launch.
Microsoft stated quite categorically at the release of the SP1 beta that the patch was not intended for the general public and that it would not provide any support for it.
The Windows 7 service pack will not contain any new functionality, focusing instead on security updates. Similarly, SP1 for Windows Server 2008 will include security updates, but Microsoft revealed that it will have enhancements to existing features and a few new ones.
These include RemoteFX, a package designed to bring 3D capabilities to remote desktops, and Dynamic Memory, which allows users to "adjust memory usage without sacrificing performance", according to Microsoft.
Earlier this month Microsoft removed support for Windows XP SP2, suggesting that users upgrade to Windows 7.