Where iPhones were once built to get out of the way of iOS, now iOS is built to get out of the way of apps.
It's hard to believe today, but the first iPhone had no third-party native apps, jailbreaks excluded. The App Store's 2008 launch changed everything, but sometimes felt like it was grafted on to the original vision for the OS.
One of the things that's changed with iOS 7 is the extent to which apps are integrated with the operating system. Full background multitasking and a more unified design language support Apple's stated goal of achieving a more content-centric experience, as does the fact that the App Store itself has (finally) become a native app. With this foundation laid, I expect future updates to expand the scope of what apps are able to do (within reason) as Apple continues to develop iOS into a full-blown alternative to mass market PCs.
Core OS design decisions are now being made with apps in mind, and I think that's going to be a very good thing for developers and users going forward.