As far as I know, historically, dual cameras have been used like our own eyes to create stereo and 3D photos.
It means both cameras needs to be side by side. All good on the new iPhone 7 for vertical shooting but what happens to the cameras when the iphone is in landscape mode and the cameras are on top of each other?
Nobody knows if both cameras are used simultaneously or they will automatically switch from one to the other in real time for wide or zoomed photos. Now about the design. Yikes. Horrible. Please don't make it protruding anymore. Not only it looks bad but the phone will never sit flat ever. Put the cameras in the center maybe.