Wannabe Cuckolds,message me

About 8 years during sex my wife said she want to have sex with another man. At that time I didn't know anything about this lifestyle. I only knew swingers. I was excited because I was thinking sex with other women. I obviously told her yes. The next day I was at work she called me and asked if I found someone. She was really horny. I thought we will have a conversation when I get back home. Later, I started the conversation and she got mad at me and she said she was just joking. I think it turned her off because she understood I was looking to have sex with women which she didn't like. Slowly from that day until today my fantasy has changed and the thought of sharing her with other men excite me alot. I have told her about my fantasy. She said NO. But over the years she does talk of fucking other men but then after while she stop and then she will restarts because she understands it excites me a lot. Now what do I do? Any advice on how to take it further. Do you think I have any chance?