Miyamoto mentions that he is working on a new Mario game for the system.
The latest Iwata Asks column gathers the original Super Mario Bros. development team: Shigeru Miyamoto, Koji Kondo, Takashi Tezuka, and Toshihiko Nakago to talk about the development of the original Super Mario Bros. game in honor of the series' 25th anniversary. Near the end of the column, Miyamoto mentions that his team is working on a new Super Mario Bros. game for the 3DS as a means of adopting new technology for the Super Mario Bros. tradition.

The comments go as follow:
Miyamoto: Yes. So, in the interests of adopting new technology for the Super Mario Bros. tradition, I am now making a new Super Mario Bros. game for the Nintendo 3DS system.
Iwata: The next stage for the Super Mario Bros. Preservation Society’s activities is the Nintendo 3DS.
Miyamoto: Yes. (laughs) I want to show everyone as soon as possible what the new Super Mario Bros. will be like on the Nintendo 3DS.
Whether the game will play similarly to the recent New Super Mario Bros. side-scrolling games on the DS and Wii or will be a 3D platforming game like Super Mario Galaxy wasn't discussed.