Nintendo will unveil its successor to Super Mario Galaxy 2 at this year's E3.
Nintendo CEO Satoru Iwata announced the Wii U game's existence today as part of Nintendo Direct, but did not go into any more specifics other than to say it would be playable at E3 2013, which will be held this year June 11-13.
Iwata did mention that it would be Nintendo EAD Tokyo--the team who made Mario Galaxy, Mario Galaxy 2 and Super Mario 3D Land--handling development of the new 3D Mario.
During the Nintendo Direct presentation Iwata confirmed that Nintendo would also be showing new Mario Kart and Smash Bros. titles at E3 2013, and that Nintendo was already hard at work on a new Wii U Zelda.
A new Wii U Yoshi game was also shown, developed by the same team behind Kirby's Epic Yarn and using the same patchwork art style. Atlus also unveiled its crossover title Shin Megami Tensei x Fire Emblem.
In addition, a new Wii U game from Monolith Soft (Xenoblade) was teased. It is being developed under the direction of Tetsuya Takahashi.
Mario's mainline 3D series has produced some of the most celebrated platformers in gaming history: Super Mario 64 in 1996 for the N64, Super Mario Sunshine for the Gamecube in 2002 and Mario Galaxy and its sequel in 2007 and 2010.
The other current Mario series - New Super Mario Bros, which is developed by a different group at Nintendo EAD - came under some criticism in 2012 after Nintendo released two entries into the series in one year; New Super Mario Bros. 2 and New Super Mario Bros. U.