He won't come back. His legs would just be too small (and they were for his last year he trained seriously).
Now correct me if i'm wrong on this but i read somewhere that,
Kevin seriously injured his back somewhere around the last three to four years of his pro career meaning he couldn't go as heavy as he wanted to on his legs and lower back.
Hence he wasn't able to bring his legs up to previous size.
As of 2004/05 he recovered from his injury and as far as i'm aware has got the go ahead from his doctor or physio to train heavy again,
but,
he's now gone to Hollywood. So technically if he wanted to, he could still be a serious pro contender even now.