I think it's safe to say that most teams require a near "best-case" scenario to win a Super Bowl. Too many injuries or bad draft picks or FA signings, it's not going to succeed like that.
In a best-case scenario for the Cowboys, Ware takes a big pay cut and has a healthy year for us, all-pro numbers, etc. Lee will go injury free as well, and play up to his high standards. Those are two big keys right there, and are achievable. Other players will also have to play up to their potential and improve, and not get hurt. A best-case scenario would be to add two quality DL to the D as well, if not more. This could be from the draft or free agency. Quality OL and WR depth would be added as well. TAdding Byrd to this group would then really give us a chance.