According to iGeneration:
With the iPhone 5, you can take apart the entire phone. A replacement will no longer be given unless there is a problem during the repair.
As far as the iPhone 4/4s goes, the most common faults (battery, buttons, vibration motor and modules) will also be able to be replaced without much problem.
This new policy should be coming mid-April, and iGeneration says that some of its readers have been advised to make bookings now, in order to get a new replacement before the new policy comes into play.
It’s worth noting that Apple’s policy towards broken iPhone screens shouldn’t change, and that you’ll still have to pay.
This isn’t official, but it would make sense, and I would imagine that anything happening in France would also apply to the US, especially something like this. So if you’re iPhone has a problem, then get to the Genius Bar now before its too late.