I'll tell you right now that Nintendo better be serious about this. The 3DS gives me hope, but for some reason I just can't allow myself to forget the mistakes of the Wii.
#1 Firstly, they expected a gimmick to NOT get old. ALL gimmicks will eventually get old, they are only a way to sell your product to the mass. Once it's sold, you must find a way to make that gimmick actually benefit the experience of your console. Which if you're a Wii owner, you know this was not the case most of the time.
#2 Like this article says, they did not build a strong relationship with with the 3rd party. In this day in age, this is a MUST; they provide new experiences to be had for those looking for games OTHER than the Mario's, and Zelda's out there. Believe it or not Nintendo, as fun as it is, people will eventually get tired of saving Hyrule from Ganon.
#3 This ties in with 3rd party support; 3rd party developers, DO NOT want to develop for last gen hardware. No I don't care about graphics, they do not make a game. But do you really think 3rd party developers want to put in the time and effort, to develop for a console that is essentially GameCube 1.5?
I love you Nintendo, but come on... Step up your game this time around. I'm tired of Microsoft and Sony getting all the 3rd party action.