Howdy all,
Some very good points raised, especially by abrannon. I didn't think of that one. If you do purchase XP Pro licences, you can install 2K with it, then upgrade to XP if necessary in future. However it can't be done with OEM licences, which shouldn't be an issue in your case. If you purchase any new systems do not purchase OEM licences with them - get the full, retail version of XP and you're free to install 2000 in place of an XP licence.
As for ksukenny, the main reason I suggested 2000 is the lower admin required from guys like us. Disabling services and changing the XP interface back to 2K's is admin!. Even after doing that, it still chews more RAM.
If MS stop selling 2K licences - who cares? Why the need to upgrade? I have clients still running on 95 as it still fulfills their requirements, as the business hasn't changed much. Unless the infrastructure somehow changes to create a need for XP there's no real reason to upgrade rather than to keep up with the Jones's.
Just my two cents.