Super Mario Stadium: Family Baseball will see a U.S. release "sometime this year" under the title Mario Super Sluggers.
Nintendo of America's Bill Trinen demonstrated the game for press in attendance, showing unique fielding mechanics in which shaking the Wiimote signals the fielders to go, and a throwing motion sends the ball to the correct base. Pitching and batting seem to be pretty much what you'd expect!
According to IGN, the cast will include the usual suspects: Mario, Luigi, Peach, Daisy, the Wario Bros, Donkey Kong, Baby Mario, Toad, Toadette, Boo, and a Shyguy. More details about Sluggers should come out sometime next week.
[Via Joystiq; press release available here]