I agree with hoops that Soliai's already had his breakout year. Shouldn't be on the list. I like Nolan Carroll too but unless a few people get hurt he's not going to have enough reps to show his stuff. He's not ready to play the nickel (should be Will Allen's spot, imo). We could see Carroll on the boundary at times when Smith's playing "rover" in dime formations, but that's a specialty situation and depending on the offensive personnel it could be Will Allen out there instead (especially against a team like the Patriots, who use Hernandez like a WR). With Crowder gone and Burnett here (and Edds healthy) I think there will be less of a need for Smith to play rover, but we'll see.
For me, the logical answer to the question is one most people have been saying: Vontae and Sean Smith. One or the other. Or both. I think we could also see Karlos Dansby have a monster kind of season. Something that occurred to me as I was watching film on Kevin Burnett is that we've been searching this whole offseason for an additional pass rusher to take the pressure off of Wake. With Burnett being such an adept coverage linebacker, it could, you know... be Dansby. He was a 4-3 outside linebacker his first several years in Arizona and is an adept blitzer and pass rusher. He had 8 sacks in '06. Without having to panic that there are no coverage linebackers on the team (Crowder and Dobbins are the pits as far as coverage goes), a guy like Burnett -- who's actually not a bad blitzer himself -- will potentially give Dansby a lot more chances to take shots at the quarterback by being able to cover the middle of the field.
One guy I'd really like to see take a big step is John Jerry. The thought of having to watch Pat McQuistan play football again makes me throw up in my mouth.