Scans just popped up of the latest Famitsu, showing pretty clearly that there's nothing rumour-like about information that surfaced overnight. As previously reported, the game will feature 12-player online support, 32 tracks (16 old and 16 new), will hit Japan on April 10 and other stuff listed here. There are plenty of new shots to look at, so off you go.
Update: More info. Sounds like Nintendo's putting plenty of weight behind this. Online leagues, global rankings, downloadable ghosts, yada yada.