As it stands now, Intel customers who need 64bit must go to Itanium, regardless of whether they are interested in all the wonderful features you enumerate here. Intel would love to keep the whole market segmented this way, because Itanium is much more expensive than Xeon. Opteron messes that up a little, Xeon64 would destroy it. Intel would effectively be competing with itself and endager the still fragile IPF ecosystem. How significant this effect would be is debatable, but your assertion that there is *no* overlap in these markets is wrong.
Personally, I think Intel is waiting for a certain level of Itanium acceptance before unleashing Xeon64, probably AMD64 compatible and latent in upcoming cores. They are quiet about it because they do not want to FUD their own product, IMO.
EDIT: The advantage of being AMD64-compatible is that they take advantage of the OS/Apps that are already ported or being ported. If Yamhill were being released in 2004 and not AMD64 compatible, then we would already know about it since they would have to give info and development rigs to MS and app makers.