I think in all honesty that is a questioned to be asked after Sheffield retires. Who knows how long his career is going to keep going and how much he will pad on his stats. s of now I say he has a decent shot. Maybe not a first ballot but maybe a second or third time around. I think 500 hr used to be the garunatee mark as you mentioned but now as more players are doing it maybe 550 or 600 will be the mark. Which in case if Sheff lasts another season or 2, he could pull it off.