In a Q&A session with investors last week, Nintendo boss Satoru Iwata touched on a the company's approach to DLC for Wii and 3DS.
The company has only just started to offer post-release content for its systems and games through firmware changes, fixes and light content, but only in a select few games like Super Smash Bros. Brawl and Mario Kart for Wii. A handful of 3DS games have also started to expand on the default content with additional levels, costumes and the like.
Iwata confirmed that the company is preparing a paid-for DLC system to be employed on the 3DS by the end of the year. Nintendo themselves are aiming to focus on "high quality", more substantial content for their systems. Stat upgrades or content keys were described as "low quality" and won't come from Nintendo, but other developers can utilise this sort of content if necessary.
The Nintendo president also re-iterated the company's previous stance towards free-to-play new games - the answer is no. He feels that it would damage the value of what Nintendo can offer in its games.