Rihanna. Taylor can't because of her Coke deal and I feel like she wouldn't do it until the following year even if she could because her album will most likely be out by then.
EDIT: Oh, I didn't know the main pop girls were excluded. I don't think anyone out of the poll options are big enough or have enough hits to headline the Super Bowl.
I'm going to say Ariana though because she has more recent hits than the others and she's talented.