When a team changes their coaching staff, there will usually be some kind of change in scheme. For the Cowboys, their offense will have some new wrinkles, but will still be under offensive coordinator Kellen Moore so fans will still see a lot of similar plays and formations from last year. On defense, though, there should be a major change.
The Cowboys under Rod Marinelli and Kris Richard ran a pretty predictable defense. There were many occasions that have been documented where opposing offenses talked about knowing what the Dallas defense was going to do on a particular play, or being able to pick up their hand signals in the secondary.