Members without a unit are people who were on rosters when a unit failed to recharter or had their charter taken. They are also people who are members-at-large of a district or council.
What happens to your people will depend on what they want to do. I do know that in most councils that members without report is a free-for-all for the various member coordinators to call and solicit for transfer.
There is a report that I can access in my.scouting called "members without a unit" that shows me all Scouts and Scouters who may be in that situation. Either the unit is folding or may be late in turning in their recharter paperwork. I am able to select someone from that list and transfer them to another unit.
So what happens to those folks whose registration expires in 3-6 months after the troop folds, and they do not want to transfer? One of my adults doesn't want to transfer to any unit or district/council POR, because he wants to restart the unit in a few months when he has more free time.