Nintendo's studios are built up abit differently than Sony's studios.
They have one giant studios, now in two locations I believe, where only two or three out of 9 assembly lines (I believe it's only seven assembly lines now) are able to make a game-engine, while the other works on assets, and prepearing the game, then they move the game-team wich have been working with lesser toolsets or outdated engines, up to the coders in the main-assembly lines, to polish the projects and engines.
It may be different today, because it's a few years since I heard how it were to work as a coder in Nintendo.
But in the end I think EAD3 is working on Zelda, while EAD2 is working on Wii Play and Animal Crossing, and EAD1 is working on Mario Kart.
The bad thing with this strategy, is that I figure it's hard to pitch a new franchise other than Mario or Zelda, while you're using the tools for the next Mario or Zelda games - especially now when they too will need to increase their budgets for HD-games.
The good thing is that the next Mario-game get's really good. :-/