That's a very good point.
If all my friends (while practicing Safe Swim defense) said "come on in, the water's perfect!" I might join them.
Here's the deal: youth will find a way.
You say "Always two adults." They say "Thanks for the training, me and my buddies are gonna keep the $28 registration fee, buy some provisions, and hike and camp on our own.
You say "Unisex". They say "No worries, my buddies (male and female) are going to camp on gampa's back nine that weekend."
You say "No purple tents." They say, "No problem. No tents!"
You say "Arrowmen: 1st Class Patch. Troop camping nights count only," They say, "Keep your sash, The ladies and I are gonna build this bridge in this camp over here."
And frankly, I'm fine with that. I'll teach them the skills, and review their plans if they knock on my door. I don't check membership cards. The boys with the cards can earn bling if they want to and when they've got the skills and the plans, go hiking and camping with their mates -- their real patrol ... not the one defined by their membership restrictions.
As far as I can tell. It's not a matter of if the greatest character-building organization this nation has ever known will be co-ed. It's a matter of if BSA will be that organization.