as the discount applies to ALL current Apple phones I would rather see this as just a measure to prop up sell through in reaction to ever decreasing IPhone sales numbers. While nobody knows when the 5S will be finally coming to stores it is quite clear that the phone will offer nothing to make it more appealing to buyers than the original IPhone 5 as the screen size will remain the same.
I don't think that is exactly true. For one, the biometric finger print unlock is something they are working on. There is a rumour that they are in the process of figuring out a film that won't interfere with it's functionality. That's just one of the new features.