Some question for season 9 ranked

So as far as I know. Most players will start at the 4th division of their current rank, and gain 30-50(?) LP for every win in the 10 games for placement. So in theory, if someone win all 10, although highly-unlikely, about what rank will they be in? and are there any exceptions to the "everyone except current Masters and Challengers goes into the 4th division" rule?