My understanding, based on some council-provided information (not from my own council, which hasn't said anything to my knowledge) is that national will send emails to the scouts' parents 60, 30, 15, 7, and 1 day(s) before they are changed, and that each of those emails will contain an option to manually renew or opt-out. The auto-renew only occurs if they do not respond. I am not saying that I agree with this approach, but it also doesn't sound like it is without notice either.
On the other hand, if the unit opts-out of this new process, the unit is charged for the renewal on the anniversary date unless they manually remove the person first. That means the unit has to get paid 60 to 1 day(s) before the renewal date, or take a gamble and either drop the scout or pay for the renewal with the hope of the parents paying. Not digging that option. You might say "well if they are absent for 60 days, that's a good clue they won't be renewing," but for many cub scouts, their renewal date will be August 31 because most join through September join nights (or at least that's typical in my district). A lot of cub scouts drop off the radar for June-August. I could see this being a big problem.
From my perspective, both options have their drawbacks.
Sounds like we agree that this is the most likely scenario. I just wish I could get a more definitive answer.