Give Apple a little more credit.If they do include a fingerprint scanner, I don't care absolutely at all about any other features they include, even a 50mp camera 1 week battery and tv sized screen, I will not be upgrading. With all the news lately, I do NOT want apple scanning my finger prints and sending them back to their servers / selling information to 3rd parties.
Apple will not store your fingerprint on the device, much less a server. Apple will use your fingerprint and other biometric data obtained from the sensor (such as skin density and vein patterns) in conjunction with information unique to your particular phone and/or iCloud account to create a password key -- the equivalent of a very, very, very long alphanumeric password.
Developers will not have direct, low-level access to the hardware to grab your fingerprint. However, developers should be able to call an Apple software routine that would generate a password key (I.e., a long number of 1s and 0s) based on the unique combination of your fingerprint, other biometric data, and the device hardware.
A fingerprint sensor is key to (a) corporate and government customers and (b) mobile payments. Corporations and government agencies currently require 8-12 digit alphanumeric passwords to unlock a phone; a fingerprint reader would eliminate these passwords, if properly implemented. Mobile payments haven't taken off because of concerns over security; a fingerprint reader, or a pin combined with a fingerprint reader, would largely address those concerns.