In my opinion,gesture or virtual button can replaced back button ,such as sweep left to return ,sweep down from the top to close the app just like win8 .Developers can integrate them in their applications .With gesture and virtual button ,there will be less mis-touch .And if there aren't three button at the bottom ,it's more convenient to out the action bar (sweep up from the bottom to out it).
I hope you can understand me and like my work .It's my first Ps work .