I'm very optimistic that the offensive line will be very good in 2007. Primarily because C Scott Wells just finished his first season as a full-time starter, and Gs Jason Spitz and Daryn Colledge just finished their rookie seasons and both were full-time starters too. Plus the turnover in the coaching staff with the departure of offensive coordinator Jeff Jagodzinski should have a minimal effect since the Packers promoted from within. Now the offensive line coach, Joe Philbin is the offensive coordinator, and the assistant o-line coach, James Campen, is the o-line coach. Additionally, there hasn't been a change in the blocking scheme which should give them another advantage.
Looking around the NFL, the Packers situation is similar to Philadelphia's offensive line. In Philadelphia, they ended the 2005 season with one rookie at left guard (Todd Herremans) and one player finishing out his first full NFL season after blowing out his knee in 2004 at right guard (Shawn Andrews). Their C Jamall Jackson had spent his first two seasons on the sidelines behind C Hank Fraley, but got his first opportunity to start in 2005. At tackle, Philadelphia started two veterans (Jon Runyon and William Thomas) that had a lot of starting experience prior to 2005. All three interior offensive lineman had their first experience starting in 2005 and Philadelphia finished 27th best on running plays and 17th on passing plays. In 2006, all five lineman started all 16 games and Philadelphia finished 3rd best on running plays and 14th on passing plays. There are a lot of factors that go into those rankings, QB Donovan McNabb's injuries, players at wide receiver quitting on the team, etc., but such a major boost in rankings, especially against the run, had to have been made in large part because the offensive line played together for a full season and none of them were rookies (or first-time starters) anymore.
Ironically, according to Football Outsiders, the Packers offensive line was just as good in pass protection in 2006, when the offensive line showed a lot of promise, as it was in 2005, when it was an absolute mess. Both seasons it had the 3rd lowest adjusted sack rate, which is due in large part to QB Brett Favre's quick release and it seemed like he didn't trust his line in 2005 at all and was very eager to get rid of the ball as soon as possible. It didn't seem like he spent much time looking for his 3rd or even his 2nd option on many plays.
The Packers shot up from 30th best on running plays in 2005 to 16th best in 2006. Hopefully the o-line can jump up much higher in 2007 too, now that the veteran tackles (Chad Clifton and Mark Tauscher) are playing alongside a center and two guards that all have one full season as an NFL starter under their belt.