Angst. You should feel angst.
It looks like something she could enjoy greatly. Maybe she will let you watch as she struggles to take all of him balls deep.
You should feel excitement for both you and your wife. Your wife will love you more than she already does if you let her fuck a guy with a body like that and that big dick.
My exgf went to a party where she stayed over and in the morning just before she got home I got a photo sent to me of a very well developed young black guy fully naked. It read that this was just one of the guys she was with and it was sent from her phone
Mine would never pose for revealing pictures, so I have had to be sneaky and take them when she didn't know it. Phones with built in cameras are great for that! She's in her 60's but still looks great in my opinion.