Analyze the last paragraph of the book. What is Orwell's purpose in sketching the pigs final physical metamorposis into humans?

The last paragraph in the book has the pigs drinking alcohol, smoking cigars and gambling. Orwell shows us with terrifying clarity the change that has taken place, "The source of the trouble appeared to be that Napoleon and Mr. Pilkington had each played an ace of spades simultaneously." The pigs and and men were virtually indistinguishable. The oppressed had become the oppressor and there was no way to tell the difference,

"Twelve voices were shouting in anger, and they were all alike. No question, now, what had happened to the faces of the pigs. The creatures outside looked from pig to man, and from man to pig, and from pig to man again; but already it was impossible to say which was which."