Looking through the 3DS game pages, various people have noticed a date for an upcoming 3DS game on the Nintendo Europe website. It revealed what could be a leaked release date for the new Paper Mario on the 3DS. The release date, which may have been mistakenly put up said 'March 25th 2011'. It was then taken down and has since disappeared.
The release date for the game fits within Nintendo's schedule for the systems release, with the company stating that the system would be out no later than March next year, for all major regions.
Not much else is known about Paper Mario on the 3DS yet. Be sure to stick to C3 for upcoming news on the title.
Many thanks to Gamekyo and Squidboy for the tip