I don't know that I agree. A stable of backs with complimentary skill sets can be just as effective as one back logging 25-30 carries a game. Four of the last Five BCS Nat'l Champs have rotated their RBs ('Bama last year being the exception, though Richardson played a lot too). I expect some attrition down the road, that's just the way it goes, but there is a good range of skill sets being accumulated:
Speed
Berry
Hall
Power
Hyde
Rod Smith
Dunn (if he commits)
Combo
Ball
I think Shell would fall into that "combo" category, but I think he'll get squeezed out by Ball/Dunn in the end. I'd guess they'd take all three if they all wanted to come, but hard to see all three of them committing.
In an offense run on spread principles (with TP/Braxton), a rotation is sometimes more effective IMO. You see the horses in more pro set offenses. Obviously, if you do have that stud that is just better than everyone else, you ride him, but if you have multiple talented backs, I think rotating is just as effective.