As a non-fan, I'm curious how Cullen is going to change my perceptions of him... I'm going to seperate my Inquisitor from Hawke, but it's still hard to ignore that this was the same guy who shows up after Act 1 to lock up Bethany. And then acts smug the rest of the game.
My Inquisitor may not know him, but I -the player- do. I'll try not to be biased, but I'm curious if he's evolved since then. If he hasn't, I don't see things going well for him.
BTW, I'm not trying to act like a hater or anything. Just figured this was a general discussion for Cullen.
To be honest, I was glad it was Cullen who came to pick Bethany. Because I could be sure he wouldn't harm or humiliate her. Besides, I think she was happy in the Circle. She finally didn't have to hide who she was, she could use her talents, and she was around people like her, instead of feeling like a freak - the only mage child in the family! She could have a career too! She found ways to express herself, and she quickly gained reputation and respect in the Circle, so that she was even allowed to travel sometimes. And she was still close to her family, her mother could visit her in the Gallows. Circle in Kirkwall was far from perfect, but it turned out to be perfect for Bethany, because, although it may sound paradoxical, becoming a Circle mage liberated her. It was still a loss to Hawke, however, so I respect it if you were mad about it 
Cullen will certainly change. You just can't believe in the same values anymore after what happened. You could actually see him changing throughout DAII, but who he will be in DAI is difficult to predict for me. I hope he'll stay sane at least 