Been lurking and waiting for awhile now, so I figured I would throw my 2 cents into the pot here...
I spoke with a rep at the store this weekend regarding this very thing. I am currently 14 months in on my contract and am not due for an upgrade for another 4 months.
I was told by the rep that I can in fact get the phone at that price. The only stipulation that he gave was that they would have to charge me an $18 upgrade fee, but other then that the phone would not be 'up priced' for existing customers...
Granted, since I am so close to the upgrade time period he may just be doing me a favor by waiving the 18 month limit, but he believed the 499 and 599 price would be across the board for anyone wanting the phone.
Makes sense to me though.. since a data plan is pretty much required, anyone wanting one will be putting more money into AT&T's pocket via the Data Plan anyway.
Good Luck to all of you on the 29th!