The problem sony has is how to differentiate different models. If they want one at 599, how do they sell a 399 model at the same time? Most people would just buy the 399 and the 599 one would rot on the shelves. That is probably why they did away with the 20gb version.
The 20gb without wireless controllers was an easy sell, but the unit costs were about the same as the 60gb one so Sony just took a bigger loss on the unit. There was probably $20 in difference between the units in build costs, but $100 in price, so Sony essentially just loses $80 more selling it.
If they come out with a $399 version how are they going to cripple it enough to save on manufacturing costs to the point where they at least lose no more money than the $599 cost? Saving $5 on the disk, $15 to cut wireless, $10 on the game not being included is $30, a very long ways away from the $200 difference in price.
The best thing Sony could probably do is introduce the 80 gb model for $499. Or start it at $599 and as soon as all the 60s are gone, make it $499. The same problem exists, how do you convince people to buy the 60 if the 80 is the same price? Most people do not know backward compatibility is reduced...
If by Christmas they had a $499 80, and they perhaps they could do a $399 non wireless, smaller drive, and no game for $399 and just eat the $70 as a marketing ploy. People would still be tempted to get the $499 one, after all they see the game being worth $50, so $50 more for wireless and the bigger drive is probably easier to swollow.