I have a hard time seeing this as anything but very pessimistic. I think that Orwell sees the whole society giving in to totalitarian government and ceasing to resist that type of government.
In this book, Winston and Julia were the only people that we saw truly resisting the Party. If Orwell is going to be optimistic, it seems to me that some good would have had to come to them or from them. But it does not. Both of them give in to the Party and Winston even comes to "love" Big Brother. So both of the rebels have given in and the Party is unopposed. Not very optimistic to me.