Hart is 99% sure he'll be back, and the fact that he personally lobbied Jake Long to come back is a good indication that he's 100% sure he'll be back.
Henne and Crable will be back because they have to be.
Branch is still undecided, but outgoing senior Lamarr Woodley has said Branch hasn't said he'll leave, implying that he'll stay. We'll see. Branch has a personal interest to come back because he did not have a very good 2005 campaign and will need to establish some consistency (see Ernest Shazor and Pierre Woods). He also played very poorly against Ohio State.
Henne reminds me a lot of Jake Delomme. Carolina is a perfect fit for him. He'll need to improve his vision and play calling abilities next year but I think in terms of playing well under pressure he's surpassed Brady Quinn. His one glaring weakness is his inability to throw a short ball with any kind of touch, but he does have a big arm. Like I said, almost a Delomme clone.
Honestly, Hart is not a big-time NFL prospect. Michigan doesn't have a very good rep with RBs in the NFL (Thomas, Perry, Biakabatuku), mainly because they benefit from NFL caliber O-lines (Jake Long won't be the only OL playing on Sundays). That's not to take anything away from Hart. He's our most important player because he makes people around him better. You need a guy like him in the locker room for his leadership qualities. But he simply doesn't have the size or speed to be a first option RB in the NFL. He'll be a very reliable second RB, most likely a good fit on a team competing for a championship. He and Jeff S. are in the same boat, I think.
As far as next year's team, we will indeed be loaded on offense. Henne, Hart, Long (along with 4 other quality OLs), Manningham, Arrington, Butler (a hidden gem at TE), in addition to RB Brandon Minor, who WILL share time with Hart next year because of his speed.
Defensively, we're in excellent shape up front, Branch or no Branch. Brandon Graham will replace Woodley and I see zero drop off there (Graham was considered by some to be the #1 prospect in 2005, but unfortunately for him he didn't see any action this year because he's in Woodley's position). The main issue will be the secondary. Leon Hall is gone, and someone is going to have to step up to be a shut down #1, either Sears, Stewart or Trent. All three have good physical skills, but have yet to display any sort of consistency. And even if Ronald Johnson commits, he probably isn't ready to step in right away. Mouton is talented, but unproven at SS. He'll replace Prescott Burgess. Ron English will need to find a balance between his strong DL/LBs and the secondary. I am confident he will find the right mix.
Based on what this team is already saying, I am sure they are hungry about next year. They want to win a championship because they feel they deserve it. Beating USC will be a springboard, hopefully the same way OSU's thrasing of Nd was to them last year. In many respects, the 2007 team is very much like the 2006 OSU team.