In my opinion, the next to the last paragraph of the book implies that Winston has completely given in to the Party. He has totally bought into what it has to say -- he now loves Big Brother and everything that he stands for.
We can see this because of how Winston is thinking. He is thinking that he used to be "sinful" but now is as white as snow. He has gotten to be this way by confessing whatever it was that he had done wrong. Now that he has confessed, he feels that he is clean again and he is fine with the idea of dying.
That implies to me that Winston has bought into the Party's line. He has accepted that what the Party says is true and that what he should want most is for the Party to approve of him and his actions and thoughts.