How does your wife's boyfriend treat her? Is he showing signs of abusive behaviour towards her? I would think that it was much more likely an agreed upon relationship dynamic between him and his wife if there isn't any evidence of the same kind of behaviour between him and your wife. I would, however, keep an eye on how you're wife is doing and address it with her if he begins mistreating her.
Everything will be ok in the end. If it's not ok it's not the end.