Nintendo, IMO, need to suprise everyone with a new kick ass handheld that does something new. They need something new that their competitors can not easily emulate and that suprises and excites players. Following the path of Sony or Microsoft is not the way!
He's my idea for a product that could offer them the type of market disruption they need. Imagine a new portable system focused on sophisticated shared Augmented reality experiences, where each players system (some sort of tablet/controller looking device) acts as a virtual window into the game world (which is overlayed onto the real world). As you move the system around you get a different view into the world- so it appears like an ar hologram of sorts.
This type of game system would be ideal for Nintendo's software which is focused on local multiplayer type games.
Imagine up to 4 players sitting around a table/on the playground in a circle facing each other, each with his/her own system acting as a window into the same game world, while little 'psuedo' holographic marios and peaches beat the crap out of each other (smash bros), compete in mini games like looking for bubbles to poop, aliens to shoot, etc (mario party), compete in duals (pokemon). Plus anyone with the system could come up and watch in spectator mode or request to join or to be next to compete!
Or as an alternative, Nintendo could make something amazing! Something none of us would think of, but that makes me smile like a big 37 year old kid when I see it 
