Optimism --
As bad as some moments were last year and despite a decimating run of injuries (especially on defense), the Cowboys were very close to making the playoffs. If Dez Bryant's hand doesn't land partially out of the endzone, maybe just that would have been enough for the Cowboys make the playoffs.
So if you accept the premise that the Cowboys were very close to making the playoffs, then a small positive change here or there could be enough for a winning record and a playoff berth.
Garrett's bright red head clearly wasn't big enough to wear two hats (head coach and OC). I really do believe that the team will be better off with Callahan as game day OC.
Although it isn't saying much, I think the OL will be better than last year. If nothing else, the young backups have now had a year in the weight room so they shouldn't be as hopeless this year. Beyond the OL, I am confident that the rest of the offense is good enough to be competent and competitive.
If the LBs stay healthy, I'm confident they'll be a strength. The CB shouldn't be a liability and may be a strength.
I think a reasonable case can be made that the team will be modestly better this year. And if they are modestly better, that should be enough for them to get into the playoffs.
Pessimism --
The soul crushing reality of recent seasons. Some losses were so excruciating that it was almost comical. It has been demoralizing. I'm not at all confident that this team knows how to win or that it can tolerate success.