With iOS 7 beta 4 available to developers, word is out that the newest test version of the iPhone and iPad operating system includes code for a biometric sensor. That helps back up the idea that the next iPhone will include some type of fingerprint scanner, but it's most likely for phone security, and not a mobile payment system.
The code for iOS 7 beta 4 includes a component called BiometricKitUI.axbundle, and code that includes text stating "Photos of a person holding an iPhone with their left hand while touching the Home button with their thumb." From that we can surmise that the biometric sensor will be built into the iPhone's Home button.
While the idea that you can make purchases in stores simply by touching your iPhone's home button sounds great and certainly would be convenient, it isn't likely that's what's in store -- at least not yet. Using your iPhone as the payment mechanism requires deals with retailers, and so far there haven't been any leaks hinting that Apple has been negotiating with companies to make that happen.
That said, if Apple were planning on using a biometric scanner as part of a mobile payment system, it could start with companies that already have payment apps for the iPhone, like Starbucks. The Starbucks app displays a barcode, and also through Passbook, that baristas scan to complete your purchase. Linking the biometric scanner to Passbook would add an extra level of security to keep people from spending your hard earned money on lattés without your permission should they get ahold of your iPhone.
Which brings us to the more likely use for a biometric scanner in the iPhone: security. Linking your iPhone's passcode to your thumbprint would make unlocking your phone as simple as pressing the Home button. It could also handle authentication to enter logins and passwords on websites, essentially becoming your biometric password. Including a way for third party apps to use the biometric sensor would mean developers could use the system for their own authentication instead of requiring users to continually reenter passwords, like in banking apps.
Apple will most likely bring its own mobile payment system to the iPhone, just not yet. It'll start with a system-wide biometric authentication and then add payment services later, and when it does, that will be handled through iTunes, just like the App Store app does when you use your iPhone to make purchases in an Apple retail store.
For that, Apple will need deals in place with retailers and that requires negotiations. Once Apple gets biometric authentication into users hands it can start working beyond security and into mobile payments. Those deals will come, but first Apple will start with biometric authentication, and if the hardware is ready to go, that could come as early as this fall when new iPhones ship.
Apple isn't saying yet when new iPhones will be available, or what features they'll have, but thanks to the code that's tucked away in iOS 7 beta 4, we know that the company is seriously looking at adding biometric authentication to future iPhones. Considering Apple is promising product announcements this fall, and that's also when iOS 7 will ship, we may get to retire iPhone unlock codes in favor of our thumbprints in only a couple of months.