The "Casual" and "Hardcore" debates is complicated because the terms are interpreted differently by different groups of people, and in most situations there is the assumption that "Hardcore" is better than "Casual" ... As always I will use "Core" and "Non-Core" gamer where the "Core" gamer refers to the traditional gamer.
Nintendo is still heavily focused on the "Core" gamer and we can tell this because in a bit longer than 1 year on the Market they will have released The Legend of Zelda, a Mario Platformer, a Mario RPG/Platformer, Metroid Prime, Super Smash Bros., a Fire Emblem game (tactical RPG), Super Smash Bros., Battalion Wars (a RTS/third person shooter), and many more 'conventional' Nintendo games.
At the same time Nintendo is targeting "Non-Core" gamers (whether they're lapsed gamers or new gamers) by producing low budget games with unconventional gameplay. The cost of development of the Brain Training games, Wii Sports, Wii Fitness, Electroplanktin and Nintendogs is far smaller than any of their core games and I suspect that the combined development cost of all of these games was less than the cost of one of their "Core" games.
Where Nintendo has an advantage and is heavily misunderstood is that many of there games appeal to both "Core" and "Non-Core" gamers; games like Mario Party, Wario Ware, Animal Crossing and Nintendogs appeal to a wide group of gamers which is (in part) why they sell so well.