Well I can honestly state that when I approached my hubby about exploring poly, I had met (re-met) someone who I was interested in attempting a relationship with. I would never have brought up the topic if I hadn't discovered it about myself due to this re-meeting. Also, I would never have cheated on my husband, but we are lucky enough to have always been able to discuss anything and everything from our fears to our fantasies and desires.
So, in my case, yes I wanted to pursue a relationship without guilt. I feel this is a much better idea than the "easier to ask for forgiveness than permission" idea, especially if a person discovers their poly-ness after being married (like myself).
Life is about the journey and not the destination,
so what better way to know life
than to wander all the roads and paths set before you.