I recently had a roadmap meeting w/ HP/Compaq and they don't have any Unix planned for any Intel processor other than the Itanium (II)

Hmm, what roadmap was this? The only one I can think of would be the migration of the Alpha and PARISC based OSs. The HP/UX Tru64 mess will definitly be an Itanium only OS (same for the newer versions of VMS), but the IA-32 line should continue to support what it does today. Officially, Com^H^H^H HP supports Linux (including quite few open source drivers lately), SCO Openserver 5 (and probably the upcoming 5.0.7), Unixware 7 and 8, and Sun Solaris. Variants of BSD tend to work, but aren't officially supported unless your company name is Yahoo. Enough revenue is generated on non MS destined Proliants that it's doubtful the existing support level will ever drop. I don't have numbers on the Unix deployment, but 50% of all machines running Netware are Proliant boxes.

Linux seems to me the most likely candidate for it first, due to the fact that Compaq already has developed drivers in that area for PCI, and the 2.5 kernel is making it even easier for any bus to have a hot plug handler (http://linux-hotplug.sourceforge.net/).

and who uses SCO?

Quite a few people actually. I see indications that SCO OSs (namley Openserver 5) have a higher percentage of the Proliant marketshare then Solaris.