There is no set date, only a projected year for the release of Zelda Cube. According to the 50-second clip that Nintendo released at SpaceWorld 2001, the game will be released sometime in 2002. The date was originally projected at the end of this year, but that is obviously not going to happen now. And, after shooting up to 2004 and 2005 on some occasions, the date has been brought back down to 2002. Nintendo seems to be making some good progress with this game.
Bottom line: As of right now, expect this title in '02.