I'd say that was a successful conversation. I don't think he realized going into it that he'd be allowed to continue his voyeuristic activities with your approval though. Of course, the variable in all this is his wife. What if she sees what's going on at your pool and starts keeping a closer eye on him? What if she catches him? I suppose we'll see how all this pans out as time goes by but this could get rather interesting.
And now the seed is planted with him about an opportunity to see your wife up close and personal. Don't think for a minute that he's not scheming a way to make that a reality....lol. If he was shocked about Mr. John coming over to ask for a key, how do you think he'd react if he knew how Mr. John bartered with your wife about his cameras? I don't think you have to worry about him though since you've conveyed your displeasure with pics being taken of your wife and her friends. I believe he understands that would most likely result in another less pleasant conversation.
I hope your wife doesn't let this ruin her pool time, though. And how do you think her friends will react when they find out they may be watched by your neighbor and most likely have already been seen? They weren't around for the Mr. John days so this will be new for them. Given how they've opened up to showing off (and more) to you and some of the other hubbies, it might not be a big deal for them....just a new opportunity to show off. Only time will tell.
The main difference with this and your wife's other exposures is that most of them could be played off as accidental or inadvertent. Since you've confronted your neighbor, the accidental or "not knowing" aspect is gone. Now if she lays out nude, she will be knowingly allowing herself to be watched. As far as she has come from the beginning, this may be a natural progression for her and she won't have to use the crutch of accidental exposure anymore. I hope she doesn't overthink this like I am and just goes with the flow. If you're totally cool with this, make sure she understands that. She's going to be watching your reactions very closely and if she thinks for a minute that you're unsure about this, she most likely will be a lot more hesitant to go forward. I'm not telling you anything you don't already know, just my typical overthinking
Thanks for the update and looking forward to the next adventure.