I agree with all that. Having John return from months or years spent in the future would negate the impact of the finale. And I also don't want him to return at some point later to save the day.

For this set-up to work, I think we need to see Sarah's struggle with the fight against Skynet in which John is no longer her focus. in other words, she needs to find herself — find her reason for fighting beyond changing her son's fate. And I think we need for John to come back with a sense of purpose. He's always been told who he is, but he's never had any reason to choose that path for himself. Now he'll have one.

I know I've said Sarah failed because she didn't stop judgement day, but I think you're right that she doesn't end up a total failure. That's why I'm hoping that if we're going to spend some time in the future with John, that we'll actually see some positive results of her struggle. Maybe judgement day did happen later. Maybe machines are less advanced in that future. if we don't see that she accomplished something positive in his absence then it really will amount to him saving the day when he returns.

So season 3, I think, is going to be about mother and son finding their purpose independent of each other, but also finding out that they are much stronger when fighting the good fight for the sake of humanity together.