Remember kiddies: If you're hoping to pick up an iPhone 4 and take advantage of Apple's free bumper offer, you'll need to do it by tomorrow. You'll then have 30 days to claim your bumper using the free app. Unless they decide to extend the offer, of course.
The September 30 cut-off date seems rather arbitrary. Unless Apple was planning on changing the phone itself, there's no reason why people who buy the phone from Friday wouldn't experience the same reception issues that led to Apple offering the free bumper.
Of course, whether or not Apple does change the phone, and whether or not Apple tells us they've changed the phone are two completely different things...