Interesting thanks. I figured that might be the case but I didn't want to lose my original promo by canceling it, then not have the second one show up either.
If you change your mind and want to trade-in another game, make sure to CANCEL the order with the promotion first, then choose the other game you want to trade-in to Amazon and the promotion will appear again. You need to cancel though yes or yes, otherwise it won't appear again on a different trade-in until you cancel it (I tried it when deciding if I should trade in God of War 3). And no, you won't lose the promo (:
Edit: I meant GoW Saga