It's the economy, stupid
Jeez, when are Nintendo going to get it? We're in a global recession. For a family with three kids looking to buy three portable gaming devices it's a choice between three 3DSs at £575 or three 8GB iPods, which can do a dozen things the 3DS can't, at £500.
That hardware price discrepancy alone would be bad enough for Nintendo, but when you factor in the cost of three cartridges (£70) against one App Store download synced to all three iPods (59p on average, a couple of quid at most, FREE for many games) it's a complete no-brainer.
Unless they bring forward plans for the eShop and develop an infrastructure that allows developers to sell cheaply and in bulk, like Apple does, Nintendo will find the market gets a lot worse before it gets better. And 3D gimmickry isn't going to change that.
Nintendo will always have a core following of Mario and Zelda fans for whom only the licensed stuff will do, so there will always be some sales.
But the rest of us aren't confused, Nintendo. We just can't afford your toys any more.