I hope it goes well for you. I'm in a similar situation with a wife of 16 years. She's been open to me in online relationships/playtime with other women, but not real touching.
I'm now trying to get her used to the idea, but going slow.
Is there some reason you want a change? Needs not being met? Falling for someone?
In my case, my wife just can't provide the attention (not only sexual) that I need to be happy, and if she tries she just gets overwhelmed. It's an introvert/extrovert situation, so giving me limited freedom was a great compromise. Things changed when I found someone I wanted to be in a deeper relationship with, though I have no interest in ending the relationship with my wife.