I think this could be really interesting and potentially could lead to Rumple actually becoming genuinely good.
Although Rumple seems pleased that Belle is seeing things his way, he doesn’t want her to be like him. I think things are going to start happening where Rumple will see that Belle is being corrupted by the darkness. He’ll have to make a decision whether to stay as he is and let Belle be dragged down to his level or whether to pull himself up and become good.
Belle is his “flicker of light amidst an ocean of darkness” and he’ll realise if he doesn’t change for the better, that light is going to be snuffed out.