Yes; according to James Cameron; Judgment Day, the nuclear war and Skynet are completely eradicated from all future timelines by the end of this movie:
Basically, what I wanted to say in Terminator 2 was that everything is meant to be a certain way, everything has already been written. You can call it karma or destiny, whatever. So I asked myself a hypothetical question: what if you could you grab a line of history like it's a rope stretched between two points, and just pull it out of the way? If you can pull it just a little bit out of the way then cut it at that moment, maybe you could change it and history could go in a slightly different direction. Like the catastrophe theory. If you could actually do that you would get a future that no longer exists except in the memories of the people who are here now. They have a memory of a future that will never happen, which is curious, because it defies our Newtonian view of the world. But couldn't it be possible? That became my point of departure. It's like the Terminator is an anomaly of our time because he's the only one who has memories of a time that will never exist. His particular future does not exist anymore.
However, this was changed in Terminator 3
, and in the accompanying television series, neither of which were made with any input from the writers of the first 2 films. T3
introduced the idea that Judgment Day is inevitable; it was merely postponed when Cyberdyne was destroyed. Humanity will eventually seal its fate by continuing to develop artificial intelligence, which one day will overthrow mankind. Cameron did shoot an alternative ending almost 40 years in the future, where Judgment Day did not happen and the Earth was safe, but he deleted it because it was too cheerful compared to the rest of the movie, and not in line with the powerful message of the movie: that the future is not set. He chose a more ambiguous ending instead. However, we must also note that due to the films after T2
, we must look to the predestination paradox to explain this answer. The predestination paradox explains that whatever has happened was meant to happen. A time-traveller attempting to alter the past in this model, intentionally or not, would only be fulfilling his role in creating history as we know it, not changing it, or that the time-traveller's personal knowledge of history already includes his future travels to his own experience of the past. Effectively, it means this: the time-traveller is in the past, which means he was in the past before. Therefore, his presence is vital to the future, and he does something that causes the future to occur the same way his knowledge of the future knows has already happened. What this means is that Judgement Day never really happened in 1997. Sarah Connor said that it would be in 1997 because she did not know what would happen in the events of T2
. So, conclusively, if we look at the Terminator
saga as a whole, the answer to this question is no. When time-travelling happens in the Terminator
saga, nothing really changes, because what is done in the past has already affected the future in which the time-travellers came from.