Isn't the whole point of the Wii that it's an accessible console to non-hardcore gamers to play.. Therefore, do their market really want to have to upgrade to get the latest games? I would have thought this move would alienate customers.. If they wanted next-gen consoles and amazing games, they'd get a PS3/360.
Pretty much all of the DS upgrades seem to have faired well... I wouldn't call that particularly hardcore either so if it can work there it can work again. The same goes for Apple products really, you can be a casual gamer and still get hyped about the latest gadgets. I'm sure Nintendo are dreaming up a million ways to convince people they absolutely need this latest console.