When did these apparent shortages start? They certainly aren't reflected in the sales figures for the past couple of weeks.
Also the whole 2.X millions of PS3s that couldn't possibly sitting in warehouses could very well be stock for the release of a revised model. Sony certainly had plenty of stock ready for the release of the Slim and if one could have looked at the shipped versus sales data in the couple of weeks prior to it's release there would have been a huge discrepancy. I'm not suggesting anything of that magnitude but the same principle could apply.
It would be a curious move if anything new was coming from Sony. Obviously the black Wii is due in the US sooner or later but I would expect that it would sold alongside the white one and not as a replacement.