Nintendo has recently published pictures on their Japanese website showing a variant of the Wii Classic Controller -- the Wii Classic Controller PRO.  This new controller drops the Super Nintendo Entertainment System (SNES) style and goes directly to the Game Cube one, with the left arrows and the thumb joystick having been inverted:

As you can see, ergonomic grips have been added. Furthermore, the thumb joysticks seem to have been moved further apart from one another. The shoulder buttons have also been relocated. However, there is still a wire, which means the controller will need to be connected to the standard wireless one, much like the first Classic Controller.