What do Microsoft’s plans to scrap SP5 for Windows 2000 mean? Well, in a nutshell it means that all the security enhancements built into Windows XP SP2 will never make it to Windows 2000. Instead of SP5, Windows 2000 will be receiving an "Update Rollup" some time next year. This will be the final update for this OS, with none of the enhanced XP SP2 stuff making it to Windows 2000 ever.
"The enhancements introduced in Windows XP SP2 will not be back-ported to Windows 2000, as this would require a significant rearchitecting to a large portion of the Windows 2000 code base."
Microsoft's official line seems to be that the decision has come about because consumer feedback has indicated that Windows 2000 customers would prefer stability to new additions, but this in effect could spell the beginning of the end for the OS, as it heads into the same blue yonder as Windows NT4.