There is not alot of info at the moment but alot are speculating that Nintendo is planning a Wii successor called the Wii HD.
As the name suggests, the gaming console will support high definition content. Its definitely going to take a pretty big overhaul to the Wii hardware to truly render high definition graphics (hint hint). Although Nintendo has proved that "hardware" isn't everything.
Like its current predecessor, its focus point will be on the controller itself. It will have backwards compatibility and focus on digitally distributed content.
