It would take an act of GOD to make Dudley change! Even after the Dementors made him see what he was truly like I don't see him changing ! So divorcing his wife when she sees the Leaky Caldron is something I'd expect of him. Also beating the " freak" out of his own daughter when he learns she's a witch is as well. After all, isn't that what his father taught him was the right thing to do?