The biggest risks that I faced of her leaving me always came from men on my social circle. Like the time a "good" friend found time to chat with her alone at a BBQ and suggested to her that he would like to meet for coffee one day and "talk." There was the time we went to a wedding of a friend, and a friend of a friend kept finding opportunities to chat with her, or compliment her dress, or bump into her circle of friends on the dance floor. And then there are always guys at her work who ask if she's going to happy hour, or if they can get together to discuss a work issue, or if she would likes a certain kind of cuisine because a new restaurant opened up and he is going to run out there at lunchtime.
These guys are opportunistic bulls, or guys who just want to get laid. They have an attraction, and maybe even sense that she may not be getting all her needs met at home. These guys are more likely to "fall in love" with her if she gives them attention. She is also more likely to "fall in love" with one of these guys because they are all in the vanilla world of pairing up and becoming couples and being life partners. These kinds of situations are your biggest threat for convincing her to change her life and leave you.
Any relationship takes communication, understanding, acceptance, and a whole lotta work. This applies to all couples, no matter if they're vanilla or into LS. In that sense, the risk of loosing your wife over an attractive black dude is equally great, regardless how open you're with your sexuality.
It seems that sometimes in our effort to celebrate the cuckold relationships and how rewarding they are for all parties involved (wife, bull & cuck), we tent to forget mentioning -at least enough- that the constant battle with emotions is real, and it takes a lot of effort, resilience, trust and respect to finally work on our favour. I know a lot of non-monogamous relationships that failed miserably after just a couple of years, because they'd lost their balance and mutual respect. Equally there is a great percentage of vanilla relationships failing, but realistically, it's rarely the opportunistic douchebag who tempts a wife, but a dysfunctional, unhealthy relationship that's a matter of time to be compromised and succumbs to temptation.
Some might say that loosing your wife over another man is a typical "weakness" of a beta man who lacks confidence and the alluring "bad boy" aura. Those guys who're struggling being firm with their boundaries, smart but no competitive, trustworthy and loving but without big egos. Men who know how to treat a woman as a princess but don't have a clue that occasionally they ought to also treat her like a whore to earn her true respect and admiration.
In a degree, that's a valid assumption. There are various reasons a woman might reject or replace you, including your poor economic or social status. However, if you are aligning with the persona above, chances are you've been considered as "highly cheatable" material and the risk of loosing her over a dominant "alpha" male is imminent.
On the contrary, when it comes to cuckold relationships, even though that such a possibility is still there, your male "weakness" becomes your ultimate virtue. A woman inside an FLR is conscious of her man's inadequacies and limitations, therefore her expectations (even those beyond sex) are based on your submissive nature, not your dominance. In theory of course this sounds incredibly intriguing and hot, but believe it or not, it only takes a few bad decisions in the heat of the moment to fuck this up and loose her for good!