Downloadable content has, probably deservedly, earned a bad reputation thanks to some publishers' actions with paid add-ons, so it's quite understandable if you're worried about Nintendo's own upcoming attempts at the model. Try not to get too worked up — Nintendo president Satoru Iwata wants to assure us that Nintendo has no desire to exploit its customers with DLC.
In an interview with Kotaku, Iwata emphasised that it isn't the company's intention to make players feel "cheated or deceived" by game add-ons. Nintendo aims to offer new content that will motivate players to enjoy their games for longer. And there'll be no skimping on the initial core packages — Nintendo still wants to create full games, not intentionally hold parts back to sell later, with the belief that such a model might discourage game purchases.
And one thing Nintendo has determined as a company policy, what we are not going to do is create a full game and then say, ‘let's hold this back for DLC.' That's not our plan. We're definitely not doing that. It's an extreme example, but I think there are examples of games where you get that initial purchase — the very core part of the game — and everything else around it is all DLC. However, if you do that I believe customers will have no motivation to go out and buy the retail package to begin with.
New Super Mario Bros. 2 will be among the first Nintendo games to offer paid downloadable content in the future, with additional Coin Rush levels planned.