About as much chance of you taking your iPod Classic to the Apple store and trading it in on a new Touch.
Can you take in a Macbook and trade it for a Macbook Air? Um. No.
I don't know why we're seeing this same thread come up over and over. Why do people think they'll be able to trade in a cell phone? Does any other carrier trade phones? This was a non-subsidized phone. You can walk into any Verizon store and pay hundreds of dollars for a cell phone without subsidy too. They charge $500 for a XV6800 with a two year contract. I'm thinking if you took that back and wanted to trade it in for something that came out this month they'd laugh at you.
I'm not getting this at all. How did Apple made it unsafe or impossible for you to sell a used iPhone? Was there a mobster named Guido and a threat against your kneecaps involved? Why in the world should they offer you something for it? You can't walk up to a co-worker and say, "Hey, you commented how much you like my phone. Would you like to buy it?" Would there then be gunplay involved? There's another thread on the same page as this one about how much people have ebayed their iPhones for and where the buyer was. Apparently they managed to do it and survive against all odds.
I didn't realize life with an iPhone was so dangerous.
The only issue I see that you're facing should be taken up with AT&T if they subsidize the new phone. That will drive the value of your iPhone very low since the rumored subsidy will put it well below what you paid for your first one and people will be reluctant to buy the older phone at a price near to what a new, subsidized one would cost.