if Victor, Phil Heath, Dennis Wolf or Dexter Jackson are in the Arnold Ronnie doesn't have a chance.
Victor is only one from your list who could beat Ronnie (even if Ron is not in best possible shape). Dexter is so much smaller than Ronnie that he couldn't beat him if Ronnie is even at some kind of shape. Heath is not touching Ronnie for a long time (at least not if Ronnie is in shape that he thinks he can enter ASC with).
And that one cutler-hair-wannabe-albino (couldn't remember his name but it got something to do with fox or some other animal...?) ain't even capable to step to same stage with Ronnie.
All this if Ronnie has motivation to prepare properly to show - if not then it's a whole different story... but I assume he has if he decides to compete again!