After watching a dominating performance on Saturday night against Seattle, it seemed likely that the Packers will have a lot of momentum going into the regular season. However it really doesn't mean much.
Last preseason, the Packers had a dominating 38-10 win over Atlanta during the second preseason game in Lambeau. Rookie WR Greg Jennings was the big star of the game with 115 yards on three receptions, similar to Saturday when rookie WR James Jones was arguably the star. Versus Atlanta, RB Arliss Beach was the leading rusher and CB Jason Horton had a big interception, and I don't believe either player made the opening game roster. If you believe in the predictive power of the 2nd preseason game of each season, then the Packers are on pace for another 8-8 season.
Since one preseason game can't forecast the upcoming season, another way to look at it is number of preseason wins has some relationship to the number of regular season wins. Looking at the 1996 through 2006 seasons, it doesn't appear that this relationship exists either. For example, the 1997 Packers won all their preseason games and went onto the Super Bowl, however the 1999 Packers won all its preseason games and then failed to make the playoffs for the first time since 1992. Another example is that they won half of their preseason games in 2000, 2001, and 2005, but they won 9, 12, and 4 games in those seasons. I don't see any reason why winning half of your preseason games would hold any wisdom regarding the upcoming season.
While listening to the NFC North preview on the SB Nation Sports Report it was suggested that the preseason showed which teams had better depth. Maybe the preseason could show which teams would play well over the next couple of seasons. If you squint hard at the preseason records over the last 10 seasons, there is some truth to that theory. Looking back at the Mike Sherman era, from 2000 through 2003 they won 2 or 3 games each preseason, but in 2004 they only had 1 victory. Maybe that was a sign that the backups weren't any good and once free agency and injuries stripped several starters from the team before and during the 2005 season, it should have been obvious that the team would struggle.
The real answer is that the preseason is too few games with too many different players involved to give any indication of how good the team overall will play in the upcoming year or into the future. The reason to watch the preseason is to look at specific roster battles (no. 3 WR, running back, tight end, starting safety alongside Nick Collins, defensive tackle, kicker) and hopefully we see a good game, no matter if it counts or not.