A new report in reliable Japanese publication Nikkei will tomorrow confirm that Nintendo will itself debut paid downloadable add-on content (DLC) on 3DS in March.
The report states that the first game to offer paid DLC will be the 3DS entry of Nintendo's Fire Emblem series. It isn't confirmed what kind of DLC will be offered, but players will be able to pay for content in the same manner that they purchase software off the eShop: via either a credit card or pre-paid card.
Third party developers will reportedly begin offering paid DLC on the handheld starting from summer 2012. Nintendo's next home console, the Wii U, is expected to offer a similar DLC functionality.