you mean a 3DS(XL) stage? Well, I can't see a stage like that, but maybe I'm wrong. Besides they make already stages for great 3DS games and there are many great 3DS games, so I don't see a need to put a less impressive 3DS stage in the game. They will most likely have enough handheld games in general that they can represent with specific stages: Super Mario 3D Land, Nintendogs, Fire Emblem: Awakening, Kid Icarus: Uprising, Ocarina of Time(and soon even A Link between Worlds), maybe also Starfox 64 3D, Luigi's Mansion 2 or an exclusive game for the handheld Pokemon games. Donkey Kong Country Returns 3D, maybe even Yoshi's New Island, Dr.Kawashima and Kirby 3DS. These would be already up to 12 possible exclusive stages while only considering 3DS games, not even a single DS game. So why put a maybe a bit too boring 3DS(XL) stage in it?