Developers got their hands on the beta version of iOS 8 after the WWDC keynote, and so far, at least one pretty cool feature has been leaked out: the lock screen will feature relevant apps based on location.
So if you're near a Starbucks, the Starbucks app will appear on the lock screen for easy access. That way you can more easily pay for your coffee using the Starbucks app.
So it seems that apps that actually need you to do something — pay or show a ticket — will be featured on the main screen. Apple mentions in its release notes that it uses Location Services to recommend relevant apps: "When Location Services is turned on, the device's current location is used to recommend relevant apps on the lock screen."
This is yet another big change for Apple. It opens up all sorts of possibilities like app makers paying for placement on the lock screen, though we doubt that will happen.
It's also part of Apple's attempts to make app discovery better. There are now 1.2 million apps in the App Store, and it's hard for users to find the right app. This is another take on trying to solve that problem.