In my opinion, this announcement by Napoleon shows that he is really no different from any of the human beings. In other words, he is just as willing to exploit and abuse animals. He is not really an adherent of Animalism -- he is just someone who is power hungry.
Napoleon was originally supposed to be different from human beings like Jones. This was symbolized, among other things, in the fact that the farm was now called Animal Farm. This showed that the farm's government was different than it had been under Jones -- specifically that it was more pro-Animal.
But now, at the end of the book, Napoleon has changed. He has shown that all he cares about is getting power. He has come to be so much like the humans that he looks like them and he goes back to using the human name for the farm.
I believe this reveals that Napoleon has completed a circular transformation. That which he had in the beginning hoped to completely escape, he has created all over again.
He originally thought humans were bad along with the rest of the animals, but by chapter 10, when we see his figure through the window with the rest of the animals, we can't tell whether he is human or animal. To become that indistinguishable demonstrates that he has taken on all the characteristics of a human. These traits the animals once saw as bad in Jones have become worse in Napoleon. Napoleon has manipulated the animals and abused them.
By changing the name of the farm from "Animal Farm" to "Manor Farm", Napoleon had already broken the principles of Old Major during the Revolution. Napoleon had already broken the rules of Animalism and instead take in humanism principles. By doing that, he is trying to erase the past events of Animal Farm from the animals' mind, and is eager to cooperate with the humans. So, by changing the word "Animal" to "Manor", he is trying to tell the humans that he is eager to be like them, as seen by Squealer walking on his two hind legs, following the way humans move about. At first, Napoleon deemed humans as bad and are enemies of the animals, but due to the fact that Napoleon became more power-hungry and ambitious, he decided to work with the humans as he knew it would be to his own benefit. The ideals of the past Revolution soon collapsed, and Animal Farm ceased to exist.