Nintendo of America president Reggie Fils-Aime clarified the upcoming 3DS firmware update allowing "add-on content.

In terms of what the next system update will allow, it will allow developers to sell add-on content, and whether that's for a physical game or a digitally released game," he said. "In terms of how it will work, it's up to the developer whether they want to make it to buy new levels, new items--all of that is up to their imagination. Essentially, what we're doing is creating the framework for those transactions to happen.
He said Nintendo will take part in offering DLC for its own games, but in a manner that "whatever we sell initially, we will feel that that is a complete experience. And if that's all the consumer wants to do, that they'd be satisfied."

Fils-Aime also said he believed the Wii U's combination of HD and dual screens will "yet again disrupt the market the same way [Nintendo] did with DS and Wii." But it won't disrupt ... the Wii. Fils-Aime believes the Wii has "millions more systems to be sold." Even better, he said that there will "certainly" be more Wii games to look forward to.