I could see getting rid of the physical button if they went to a backlit touch sensitive area somewhere on the bezel.
I don't understand why people like this idea. You have to hold the device so doing this would either have you making a lot of accidental gestures which would make the device way too frustrating to use, or having to hold it very gingerly to avoid touching any place that could read a gesture, also very annoying to use.
Sure, it sounds neat, but in practice it would just make the device really annoying once you got over the "neat" factor.