The reason I have huge hope that the OLBers will improve, is because of what Pettine's system ask them for. I believe Pettine uses more one on one man coverage to allow get more one on one match-ups up front, and he uses versatility to create confusion, on who's rushing and who's dropping in to coverage.
The reason I have hope, is that of the Packers OLBers' strengths... versatility might be their biggest one, which fits perfectly with Pettine's system.
Matthews and Biegel might be more equally good at all trades, than really standing out in a single area. Perry and Fackrell aren't nearly as well rounded, but they're sorta opposites, with Perry being best when going forward almost like a DE, and I see Fackrell as best when an off the line LB... and I've always thought Fackrell is at his best when used like he was in college... he was used in coverage a good bit and then used on surprise blitzes... they had trouble stopping him because he's quick, tons of length and because they weren't expecting it because he didn't do it majority of the time.
Also I think LB Burks could potentially be the most underrated guy right now... I don't know if he'll be ready quickly, or maybe not even as a rookie... but the guy college film makes me think I'm watching a good coverage SS more than a LB. I think they'll be doing some very nice post snap rotations with him once he's ready. Like it looks like a DB is going to jam a slot WR or TE.. but instead the DB blitzes creating an overloaded blitz to one side and Burks rotates into man coverage with the slot guy.