Of course there isn't any necessity for a Wii redesign on the outside, but on the inside of the console a jump to the 45nm technology would make the console cheaper to manufacture, so it's a very logic move.
If production costs can be lowered by making the console smaller then business wise it seems a natural direction to take. And we all know console redesings boost sales, something Nintendo doesn't need right now, but maybe in a couple of years.
Technology on the Wii isn't new except the one in the wiimote, and that's in the controller, not in the console. I'm pretty sure a handheld with the power of the Wii could be made, so that means that the Wii could be even smaller, the only part that I believe can't be made smaller is the DVD drive.
