Preview at WWDC likely in June, followed by September launch.
iOS 6 Automatically Scales to Fit Taller 1136x640 iPhone Display
Thanks to some tweaks to the iOS Simulator application that is included in the iOS development tools, we were able to run the simulator at the rumored next-generation iPhone display resolution of 640 x 1136. We did this running both the current public release of iOS 5.1 and the upcoming iOS 6.0 The iOS 5.1 simulator displayed the home screen with a stretched set of four rows of icons. On the other hand, iOS 6 displayed five complete rows – as our sources said Apple was testing for taller iPhone displays.
iOS simulator at 1136x640 with five rows of icons under iOS 6 and four rows under iOS 5.1
Notably, setting the iOS simulator to resolutions other than 1136x640 does not result in automatic scaling, with the software instead simply defaulting to an "iPad-like home screen layout" different from what is seen for the iPhone. The observation suggests that there is something special about that 1136x640 resolution that suggests Apple has at least been working on an iOS 6 device supporting that screen size.