When a WS gets what they want they are typically amicable with the LBS even to the point of being friends and doing things with the family. The LBS reads this as a sign that she/he is softening and rethinking things. Then out of the blue OM/OW comes into the picture and the LBS in dumfounded.

I was on the beach one day talking to one of my BF wife. She said doesn't want to be married to or have sex with my friend anymore but she would love to be friends with him.

Look Mach you are in a tough spot. You take responsibility for your separation which is a good thing. You claim to be a changed man and have showed her your changes for three years. You have to decide when you feel you did all you can do. I am just not a big proponent of the LBS waiting around forever. Life is way too short. Only you how long to wait. I am just trying to open your eyes to the fact that if she is dating then you are not on her radar right now.