How much does it cost to upgrade on AT&T?

I bought an iPhone 4 back in Aug 2010. My contract was supposed to expire this month BUT someone stole my phone in April so I got the 4s and my contract was reset. In the event that the iPhone 5 drops, how much would it cost to break the contract and get the new iPhone?

The full non-subsidized price (or no contract price) of a 16 GB iPhone 4S is $649. The new iPhone will almost certainly have that same price when it comes out, and the 4S will be made cheaper. If the new iPhone drops next month or October, you're looking at paying full price for the upgrade-$649. After six months, you'll probably be able to get the 16 GB model of the next generation iPhone for $399-$499 from AT&T. The 32 GB model will cost $749 and the 64 GB model will cost $849 at full price.It'll be eighteen months before you can pay the fully subsidized price of $199 for the new iPhone 16 GB when it comes out.

If they don't let you upgrade, then breaking the contract will cost you a bit. You're looking at $325 for a cancellation, and then paying full price for an unlocked iPhone.