If it was supply drying up that would assume demand was higher then actual stock. Which would mean that those 2000 sold this week would of been sold last week due to having no new deliveries of the old console. Thus meaning if that was true we would of seen next to no PS3's sold this week not 2000.
Just a case of people holding off for the new one.
That's not always the case - your first point. It's pretty obvious that:
1 - normal demand for current PS3 hasn't changed as such , however supply has been removed with retailers reporting no stock to sell
2 - normal demand for new PS3 isn't known yet, but it's pretty obvious that the normal demand for current PS3 will transfer to the new model, hence those waiting for slim won't have bought this week
The result is a drop in sales due to both of the above - plus a natural drop after recent sales boost as noted by Source.
I agree that in principle you'd figure that sales would be 0 this week but in reality in retail that almost never happens. Basically there were a few hardy souls who went out and bought a PS3 even though if they waited a week they'd get essentially the same thing but smaller and with less power consumption. And due to the deliberate drying up of the existing PS3 stock available PS3s were thin on the ground.
I think some were expecting a small boost due to the price reduction for the existing PS3 - but that would only have happened if there was more supply around and a bigger gap before slim. Really IMO all the price drop did was get them those 2000 plus sales vs even less of the current model.
Try to be reasonable... its easier than you think...