I won't claim that I was in the same physical condition that WM was when he was hurt, but back some years ago (18 of 'em, to be precise), I shredded my knee, but not nearly as bad as WM did his.
That said, I don't believe he'll ever be the same. He won't have the breakaway speed he once had, but he'll still be plenty fast enough judging from his days at Miami. His knee will be troublesome for the rest of his life with chronic aches and pains, but he's still pretty damn good.
I love his patience and vision. Along with his reads, blocking, and open-field running, he's a dangerous offense weapon.
Kudos to TD for picking him up. A great move, although many of the TD-bashers would be reluctant to give him the credit due.