Position by position, the OP nailed it. But football is a team sport, so it's still a big unknown whether the guys will adapt to the new schemes on both sides of the ball. From that perspective, I think the offense will take a small step backwards or, at best, stay about the same as last year. I anticipate a pretty significant improvement on defense. The Ryan twins were totally inept at designing a scheme that maximizes the strength of the players we have while minimizing their flaws, calling plays, clock management, and general game management.
With what appears to be a tougher schedule, 8-8 seems realistic. With another year to build a better roster and get everyone acclimated to the new schemes, we could see the playoffs next season. I wouldn't rule it out for this year, but it's a loooooong shot.