It doesn't appear the Cowboys will be making significant offseason changes. Even many of the vacated assistant coaching positions could be filled by folks already on staff.
Dallas isn't expected to be a major player in free agency (you should know this drill by now). The most notable player additions will likely come via the 2018 draft class.
Without knowing who the Cowboys or their opponents will add or subtract during the offseason, we're still going to make an educated guess regarding the upcoming season.
Dallas' 13 opponents for the 2018 season are already known. We just don't know the order of how they will be played.