According to countrystars.com, the Chicks will sing the National Anthem:
DIXIE CHICKS TO SING AT SUPER BOWL FOR AUDIENCE OF 800 MILLION
If you love football and you love the Dixie Chicks, you'll want to check into the SuperBowl XXXVII telecast on January 26th to catch the Chicks singing the National Anthem on ABC-TV. Oh, and you won't be alone. More than 800 million people worldwide annually watch the event, including 130 million viewers in the U.S. Super Bowls account for the top ten most-watched TV programs of all time.

http://www.countrystars.com/news/haislop/n-update.html


Now this year, they can add one more person.