"For a long time, we have been unsure about the release dates of some of the more anticipated Nintendo 3DS games. As of today, we know that Super Mario 3D Land (previously called Super Mario 3D), and Mario Kart 7 (previously called Mario Kart 3D) will be released this holiday season."
"Super Mario 3D Land is set to release in November. In addition, Mario Kart 7 will be releasing sometime in December. It is not confirmed that “Mario Kart 7″ will be the actual title for this game."
As said in Nintendo Buzz