From the GameInformer magazine there have been inside reports saying that Nintendo's already working on their next big home console. The goals for this system is to have next-gen graphics (With HD!) and better online gaming, maybe even an organized network similar to Xbox Live. They will still be working with the motion sensing controls and work with it to make them better and give players a much better feel of being in the game.
Something to note though (and is said in the magazine) is that this is only loose talk and isn't to be taken too seriously until there's an official announcement.