2 additional seasons for The Voice

A big fan of NBC's "The Voice"?  It seems like the third cycle has just started, but it's already been decided that there will be at least two more seasons.  This is the last season for Christina Aguilera and Cee Lo Green, who will depart to focus on solo projects.  Who will be pushing those big red buttons instead?  In the spring, Shakira and Usher will join the show as coaches and judges.