There is absolutely no way the Cowboys win Super Bowl 28 without Emmitt. They may see RB as easily replaceable today but the 1993 team started out 0-2 and only won their division due to a heroic effort by an injured Emmitt Smith in their last regular season game. Besides rushing for almost 1500 yards, despite missing 2 games, he was also the Cowboys 2nd leading receiver that season.
Jerry did say the same thing about DeMarco Murray and then promptly proved himself wrong as Joseph Randle flatlined as Murray's replacement. Most likely, Romo wouldn't have been such a target that season and might have remained healthy had Murray remained with the team. In either case, the team plummeted from a 12-4 season in 2014 to a 4-12 record in 2015.