The promotion runs until the end of the year (December 31, 2013) and is valid for eight games, including Madden NFL 25, Call of Duty: Ghosts, FIFA 14, NBA 2K14, Battlefield 4, Assassin's Creed IV Black Flag, Watch Dogs, and Need for Speed Rivals. Each title costs right around $60, give or take a few pennies.
Once the Xbox One version(s) come out, you can trade in your Xbox 360 equivalent(s) and receive a $25 bonus credit toward the same title(s), plus receive the trade-in value of at least $25 for your game(s). That leaves you with a balance of $10. Sure, it's not free, but $10 per title is a lot easier to swallow than having to purchase each game at full price all over again.
What's also neat about this promotion is that you don't have to purchase your Xbox 360 game from Amazon. As long as you buy the Xbox One version from Amazon, you can trade in your Xbox 360 equivalent no matter where you bought it from.