I don't think he will have much of an NFL career.
A lot of quarterbacks get labeled a "product of the system," and I think this can apply to James, an RB, as well.
Look at the way he ran the ball with Oregon, simply sprinting to the edge and turning it up--that doesn't happen in the NFL. They are too fast. He absolutely gashes people, but in my opinion it has more to do with Oregon's marvelous offensive system than his running ability. Don't get me wrong, he is fast as ****, but in the NFL you have to be able to do everything well and one thing better than anyone else to have a spot for long. I just don't see it.