I'd be really disappointed if they did forgive him... Understand his reasons, ok, accept it, ok, but forget him... No. Just no. No matter the reasons, you don't forgive the person who killed the father you loved and who raised you with all his heart (Yona's case) nor the friend who betrayed you after all you two went together and tried to kill the girl you loved and who you know loved him.
If he did die at the end, that's fine, one can let go of grudges towards the deceased ones. But that's about it for me.
Let's see hoy it goes anyway :)
Idk abt Hak BUT Yona is soooo kind/sensitive and she can forgive Su Won easily. Beside that, he doesn't have anything against Hak or Yona, he only wanted to avenge his father. So yeah I think they will end up being together again. I'll be disappinsed if she forgive him too but on the other hand, I don't want this manga to have bad or sad ending.
I have feeling that Hak and yona will forgive Soo Won at the end OR he will die to save/protect them. I think this's how this manga will end. I hope the ending won't be sad.