Via Kotaku:

Shigeru Miyamoto has revealed to Edge that Super Mario 3DS will be completely revealed at E3 this June.  Even more important is that Super Mario 3DS will be made available sometime later this year.

Super Mario 3DS is invisioned to play like a mixture of Super Mario Galaxy and Super Mario 64.  The game is being made by the same team who created Super Mario Galaxy 1 and 2 so this game should not disappoint.  The obvious "surprise" addition to this game will be that the classic raccoon suit will make a comeback. “The tail you mentioned on the logo – it’s what you think it is,” Miyamoto said. “You probably know what’s going to happen using that character.

Miyamoto says this, “It’s a combination of Super Mario Galaxy and Super Mario on N64. It won’t convey the message if I talk to you today, but if you play it at E3 that will give you more understanding of what I’m talking about."

Of course he also stresses the importance of the 3DS's 3D capabilities, “For example, the floors floating in space: in 2D it’s difficult to judge the distance, but in 3D it’s really easy.

Most important of all was Miyamoto’s promise that the game is “completely original, and coming this year.

Nintendo's E3 keynote hasn't been given an official date yet, but it is expected to be a day or two before E3 June 7-9.