Preview at WWDC likely in June, followed by September launch.
Details on Jony Ive's 'Very, Very Flat' Design for iOS 7
Jony Ive took charge of all Apple's user interface teams last October following a management shakeup.
While the look of the updated system may be surprising to some, iOS 7 is reportedly not more difficult to use than earlier versions of software platform. There is apparently no new learning curve in the same way there was no learning curve when the iPods went color. While iOS 7 does look different, its core apps and system fundamentals (like the Lock and Home screens) mostly operate in a similar fashion to how they do today.9to5Mac says Apple's engineers are looking to add more at-a-glance information to iOS, while keeping the system easy to use for less tech-savvy customers. The article notes that Apple has looked at ideas to implement new panels with swipes from the left and the right of the screen, much like how the Notification Center currently drops from above.
iOS 7 is codenamed “Innsbruck,” according to three people familiar with the OS. The interface changes include an all-new icon set for Apple’s native apps in addition to newly designed tool bars, tab bars, and other fundamental interface features across the system.
Apple's industrial design is the face of the company for many customers and with Ive heading up both the software and hardware teams, there could be a closer connection between the devices themselves and what users actually see on the screen going forward.