The beauty about this defense is Browner won't have to if he proves incapable. We have enough guys who can line up in multiple areas. If Revis is in a matchup where he is following the best receiver, Dennard can line up on either side. Ryan can line up on either side. Even Arrington can line up on either side in a bind, though he is one you prefer to have in the slot because he's way better there than on the outside.
Browner could potentially line up at safety on occasion. I don't see it as a full-time thing, which has been suggested by some, but I will not be surprised to see him at the SS spot in some packages. BB is about versatility and using guys in multiple spots. Remember, Ty Law lined up at SS in a few packages back in the day.