AT&T has clearly stated that any iPhone purchased / activated before July 11 would receiven and "Upgrade Eligible" status to allow them to purchase the iPhone 3G for $199/$299. The key here is to have activated an iPhone and have a valid iPhone data plan on the contract. Here is the press release that discusses the "Availibility" and the July 11 date!It's like having the same phone number on two separate phones. It cannot be done. When one serial number is attached to one account it is spoken for.
I activate and sell these phones for a living. If I tried a normal phone with an IMEI on one account and then try to account it on another it gives me an error saying it is attached to another account.
And also point taken if an iPhone was bought within this close to release date they aren't going to do anything probably. Getting an iPhone a week before launch does not count for upgrade I am willing to bet on.
If for some reason this does work, I guarantee AT&T and Apple will catch on to this and put a stop to it. In my opinion if your not eligible your not eligible, wait your time period or pay the price.
It's people that cheat the system that ruin it for the rest of us all the time.
http://www.att.com/gen/press-room?pid=4800&cdvn=news&newsarticleid=25883