I hope I am wrong, but I think our defense will continue to struggle against average and above offenses. When the Packers get in trouble is when the offense runs up against a really good defense and can't put as many points on the board and the defense can't give them the support by keeping the score close.
While I understand what you are saying, "IF, the defense improves in the next 6-7 games, Pettine might have another season in Green Bay". I just don't expect to see a big enough improvement to warrant giving Pettine a 4th season.
And by IF I mean that the unit turns into a very good defense not merely solid, which of course is unlikely.