There are ominous signs that suggests that the days of Windows 2000 are numbered. Windows 2000 is still on my desktop and is working well (I do have Windows XP Pro on my laptop).
I wanted to see how the desktop system would compare to the requirements of Windows Vista. Microsoft supplies a site to prepare for an upgrade to Vista.
link: Vista Upgrade Advisor
As you can see, the advisor does not work for Windows 98 or Windows 2000. Perhaps that is a hint of things to come. In any case, it is not very reassuring.