The Pack I belong to (as Wolf Den Leader) just did its crossing over ceremony two weeks ago. There was one AOL scout who had decided not to join a troop at this time.
The 7 scouts moving to a Troop crossed over to their new units. The scout choosing not to move on, was recognized as crossing over to his parents who then presented him with his AOL patch and pin. Because I am also the Scoutmaster for one of the troops that was receiving new scouts and knew he wasn’t moving on, I brought a small gift for this one scout and made a short statement after he crossed to his parents to the effect of “All of the troops here today hope that you will continue to let the Scout Oath and Scout Law guide you in life and would be happy to have you join our ranks if you decide to return to scouting in the future. Congratulations on earning Cub Scouting’s highest award.” - and then I gave him a small gift (a nice compass).
I think he appreciated the added recognition especially after watching his fellow den-mates get a more ceremonial welcome once they crossed the bridge.
As to the dilemma your son is facing in trying to pick a troop - my troop has been having undecided AOL scouts attend our meetings as recently as last week. I’ve told them not to rush, come to as many meetings as they want, and even given them the contact info of the other nearby troops to check out. Finding the right fit is important and I’m happy to facilitate that even if that means the scout joins one of the other troops instead.
I don’t know if this is universal or just my Council, but the scouts still in the Pack aren’t forcibly promoted to their next rank until like July. Meaning, your son has plenty of time to shop around. The Pack doesn’t need to end his membership right away. That can wait until he decides where he wants to go.
That one AOL scout that didn’t cross over to a troop, he’s been left on the Pack roster so he can choose to continue to do Pack events if he wants to. If he doesn’t apply to join a new troop before summer, his membership in the Pack will end when the hard deadline comes for promoting the other dens. At that point, he can always choose to apply directly to a troop of his choice if he changes his mind about leaving scouting.