NBC's live performance of The Sound of Music will probably resemble the musical more than the movie. The musical and the original movie could be considered products intended for mass consumption as well, and one could question
how much 'religion' was present in the real-life story (though the family was Catholic). NBC is desperate for viewers and trying to capitalize on Carrie Underwood as a country-pop star, but the producers probably feel the itch to update the musical in some way. I expect there to be very little religious references.