sticky situation 😞

I really need some advice!! I met a guy not too long ago, and his situation is all types of crazy. First and foremost, he was upfront when we met and told me that he has been seeing someone for 8 years, and they are in the process of splitting up. She is currently looking for a new apartment, and he stays where he is because that's his home and has been his home before she came along. So when I asked him, are they still involved with each other in any kind of way, he simply let me know that they respect each other, it's no hostility. He said they sleep in separate rooms but they do still have sex occasionally. So I asked him does he plan on stopping the sexual connection between them any time soon. And his only answer was "we have been together 8 years, it's a process"...... At this point in his life, isn't it selfish for him to be meeting other women getting involved knowing he is still emotionally, physically, etc attached to this woman?! I mean, it sounds like he has no plans on actually detaching himself. What should I do?? Would you stay or would you just not deal with a situation like this?