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.