The date has been determined for sure.

Gawker.com has the scoop (here)

UPDATE: WeCanKnow.com (here) has two dates set: the Return of Christ (Rapture) and the End of the World.

WE CAN KNOW from the Bible alone that the date of the rapture of believers will take place on May 21, 2011 and that God will destroy this world on October 21, 2011.