“Hook will fall in love with Belle. His plan to use her as Rumple’s weak spot will break apart when he gets to know her personality. Just like she made a difference for Rumple, she will will make a difference for him.” 

Hook will _pretend_ to fall in love with Belle and Rumpy may be jealous (which I agree would be fun to see), but ultimately she will see through him. It will be too late, she will already be in danger but Rumpy will save her and it will bring them closer together.