A few recent developments have given me some ideas for the next portable Nintendo system.
The iPod now has a few games available for it.... But the control interface doesn't work for games. If the next iPod works like the iPhone, it might have some pretty good touch games available. Even better, why not build a controller for it to dock into?
The Wii already has 4 different controller units.
The Wii has built in memory, and features several non-game functions Nintendo has shunned in the past.
The DS is a great system, but it has a few faults. It doesn't have analog control sticks, so it isn't best for 3d games like Mario 64. With some games, the controller game become uncomfortable... mostly those that use the shoulder buttons a lot, such as Mario Kart DS. Though not a fault as a game system, it can't be used as a mp3/video/photo media player.
My idea is to make a Gameboy that has no buttons. It would contain a 4 inch, 3:2 touch screen, and all the necessary hardware. In this mode, you could play any game that only uses the touch screen, such as Brain Age any Kirby's Canvas curse. You could use it as a media player that has functionality similar to the Wii.
The system would come with a standard controller dock. This would look similar to a PSP or a DS without the top screen. You could also mount the screen vertically, and use it to play DS games.
Because the controller would be separate from the system, Nintendo could have an optional comfort grip, with full size analog sticks and comfortable L and R buttons. It wouldn't be pocketable, but it would still be portable.
These illustrations below aren't very well developed, and are just composites of images of existing systems to give a basic idea. I didn't show how the base would connect to the grip, and I can assure you that I don't think Nintendo should make a PSP clone.