With the resources of a company like Microsoft I am a little sceptical about non-intentional shortages. AFAIK, the other 360 models overall eclipsed the sales of elite models anyhow.
I am also sceptical of a HD DVD equiped Elite rumour as well. All mass produced HD DVD drives released so far have been half the speed of the PS3's Blu-Ray drive and a HD DVD drive within the 360 would mean the HD DVD drive must be able to speed up considerably to achieve 12 speed DVD reading speed to not result in long loading times for non-HD DVD stored XBox 360 games, this because the data density is much lower on a DVD than on a HD DVD and especially compared to a Blu-Ray disc. One disc rotation equals for less data being read on a DVD disc.
For Europe the 360 seems to be overstocked, at least the pallets at local stores shrink much slower than the PS3 pallets. Also Microsoft doesn't have to allocate many units for Japan. This all makes me sceptical of their excuses.