You don't need touch sensitive edges. You just need *proper* gesture detection. E.G. MicroB - you CAN get the swipe from right/left gestures to work just fine in portrait mode. It's just harder to get the touch to come in from "off screen" with so little room on the 'top' and 'bottom' edge.

So long as the gesture is recognized as "from-very-edge-of-screen-inwards" it's going to be virtually indestinguishable to the end-user.