We've hammered this topic a lot since his injury.
Reality is, that in terms of this decision, it doesn't really matter where he projects in the Draft, what matters is does he improve in any significant way by returning to school?
If he gets a 4th or 5th round grade, he should go pro. I love Walton, but I don't see his stock improving to a round 1 to 3 player with another year in college. Heisman watch list RBs regularly fall well into rounds 2 and 3.
If he gets a round 6 through UFA grade, it might be worth the risk to come back for another season because he could improve his stock in a meaningful way.
Those late round grades are RB purgatory. Teams won't have enough invested in you because if they are picking you that late, they probably have at least 2 to 4 other RBs in the mix they like equally if not a little better.