A few thoughts on some players...
Trent Richardson is probably going to be the name you hear the most. With Coffee going pro and Upchurch in limbo, you can probably pencil Richardson in right now for 125-150 carries this season, and he'll probably see more meaningful touches than any other true freshman in the conferece. Combined with his raw ability, the production will be there.
Reuben Randle will get all the hype, but I doubt he's one of the bigger impacts. He's a bit raw and needs some honing, and at best he is going to be the third (or fourth) receiving target in an offense that will largely be run-based and one that will still not have great QB play. All put together, that's not going to generate a lot of production.
Nico Johnson is a name you will hear a lot. He's just too good of a defender to stay on the sideline, and he'll play a ton of meaningful snaps. Ditto goes for Dre Kirkpatrick.
Darius Winston, the five star corner, is going to make a pretty big impact with Arkansas. Their secondary is terrible, and he's probably the best player they have now, period. He'll start from day one, and should be about their best player.
Eltoro Freeman at Auburn will have a big impact. Their linebacker corps really has nothing to speak of, he enrolled early after spending two years at a JUCO, and he's a very talented kid. You do the math. He should be one of their best players.
Marlon Brown's impact at Georgia will likely be limited. He played against weak private school competition in high school, so there will be a fairly big adjustment period, and at absolute best he'll be the third option behind Green and Moore, with a raw and inexperienced quarterback throwing him the ball. Again, you do the math.
James Carpenter will have a big impact at Alabama. You can guarantee he will grab a starting job immediately, otherwise Saban would have never given him a scholarship, and frankly he looks to be a stud. Combine that with the fact that he enrolled early and will go through Spring practice, and you get the idea.
Andre Debose is going to have a big year at Florida. He'll step into the Percy Harvin role, and I still expect him to be a 500 / 500 guy as a true freshman. Yes he's young, but the spread option is a relatively simple offense, and all he'll have to do is put his athleticsm to work in space.
Craig Loston will make a big impact at LSU, bank on it. Their secondary sucks, and Loston is as good as any prospect in the entire 2009 class. If he stays healthy, I'd bet good money you'll hear his name called many times in the Alabama v. LSU game this Fall.
Russell Shepard will play some, but it will be more as a gimmick player. If he has any sense, he'll redshirt and move to wide receiver, but the ego and arrogance would never allow that.
Michael Ford will probably have a bit of a limited impact. You should see him play some, and he has a very bright future, but he's going to be behind both Charles Scott and Keiland Williams, not to mention a runner at quarterback, so he's probably just not going to see the ball all that much. If the two guys ahead of him stay healthy, I imagine he's looking at 50 carries at most, and he's not getting any special attention for that.
Both Pat Patterson and Bobby Massie will have a pretty big impact at Ole Miss. They are both in positions that will easily have them on the field, starting, from day one, and they'll get plenty of attention.
Chad Bumphis will catch a ton of balls this Fall, most likely. Granted he'll do it on a team that will, if lucky, go 5-7, but he'll catch a lot of balls.