I don't think they have time for two steps of play-ins, just a single early/midweek game and have all of those winners play on the first Friday. Without extending the length of the tournament, they could enlarge the field even more, as long as they have 64 by Thursday. If they give the play-ins the extra day to only play on Friday, that would max out the potential to 80, I think. 16 first round games each on Thursday and Friday, so have 16 play-in games (32 participants) to occupy the Friday slate.
If my thinking is right, then this extra four team move is just a step toward 76, then 80.