80GB model not likely to stay at $599
I am no industry analyst, but Sony has stated that the stock of 60GB PS3 will last until christmas, which in turn is likely to mean a price drop to $499 for the 80GB model. PS3 sales will get a boost from the $100 price drop and I don't see Sony giving that up because they run out of stock on a SKU with 20GB less space.
IMHO there is 0% possibility that the 80GB model will stay at $599 once the 60GB model is phased out.