No release date yet. But listen to what the game’s Wikidpedia profile has to say:
Shigeru Miyamoto stated that the new sense of depth makes it clear where all the objects are. Gamespot, IGN and Computer and Video Games have commented on the game’s good use of 3D in the game, stating that it helps with judging distance, “heightening that sense of falling”, and giving more depth to viewing items and their effects, such as the “ink blot”. All three sites also praised the games frame rate and graphics in general, especially the fact that it ran at 60 frames per second. A new feature is how characters interact with each other while driving. Characters not only turn their heads when another racer is nearby, but make faces as well, such as “glaring”. The game was the number one most wanted 3DS game by IGN, and in a poll conducted by Official Nintendo Magazine.