I don't want to make any kind of prediction right now, but just to make a couple points:
Harris was largely a superstud in his first year due to a couple things --- 5 sacks in the second half of the year, and a very memorable first 2 games as a starter where he was in on 17 and 24 tackles against BUF and WAS.
The remainder of the year he did very well in tackles, but I think those first couple games are what made the impression in everybody's mind.
I don't recall the details on the BUF game, but I think he had about double normal opportunity in the WAS game.
I'd be interested to see his opportunity in '07 vs '08, and I'd imagine '09 would probably stack up favorably in that dept.
edit: just went and looked up a couple stats.
'07 and '08 were nearly identical in terms of plays faced by the defense at 1020 and 1016, although I should go back later and break out the games he actually started.
The biggest difference was in pass attempts faced, with only 470 in '07, but a whopping increase of 102, for 572 in '08.
Getting 5 sacks in roughly a half season from an inside linebacker is pretty huge, so I'd want to look at his role in Ryan's defense and how his counterpart was used in Balt.
That might be a stat that bounces back from a disappointing '08 in a more aggressive '09 defense.
Is it Scott playing the Lewis role and Harris playing the Scott role?