if you're looking for excitment and willing to risk,

i wish you good luck. if you're looking forward a stable life, you'd better stop seeing him. by the way, one of the reason that married women have less affair than men is that most women look for stability as they get older.
my only advice: don't believe you're the only woman he wants, please add a big "NOW". so, if you look for forever, you are gambling.
my best friend fell for a married english man when she worked in china. she belived it was just love, and she didn't expect anything from him. he was the most romatic man she met. after two years, her woman's heart told her only love was not enough. of course he never thought about divorce and to marry her. that was the end. later that very man slept with her friend, and that "stupid" girl told my friend that he thought my friend was the love of his life. when my friend told me a year later in america, we just laughed at it.
so, if you dreamed to marry him(if i understand correctly),you should be much more pro-active. you have to have a plan to let him divorce first, which as a married person, i will definetly give you no advice.