I run a couple box's, w/ 2k, they update fine , and I love them, more than the other two w/ xp pro, but not as much as suse xp was built on 2k (nt platform), secure, and none of the "pretties" to deal with.
They have released a "roll up" for 2k, my guess is the support will be ongoing for several years, simply due to the businesses that still incorporate 2k.
edit: as far as the xp pro, there are user settings / restrictions , that are not allowed the same in XP. The pro allows me to set tighter access restrictions on other boxs, while keeping usability within my local network.