Isn't Disaster: Day of Crisis being developed in-house by Nintendo? If so, I think that would probably be the first M-rated in-house Nintendo game.
Either way, I'm divided on whether I want to see more "mature" games by Nintendo. On one hand, they're one of the few development houses out there who still makes light-hearted games that can be enjoyed by all ages. On the other, I'd really like to see perhaps the most consistently quality development house out there try their hand at an M-rated game or two.
"'Casual games' are something the 'Game Industry' invented to explain away the Wii success instead of actually listening or looking at what Nintendo did. There is no 'casual strategy' from Nintendo. 'Accessible strategy', yes, but ‘casual gamers’ is just the 'Game Industry''s polite way of saying what they feel: 'retarded gamers'."
-Sean Malstrom