That would the obvious crux of a third film, they keep on avoiding. Which would take place during the war, but instead of time travel, we have flashbacks.
- John thinks they prevented Judgment Day. Sarah doesn't.
- Sarah using logic realizes that Judgment Day has to happen for John to be born.
- This splinters their relationship again, leaving them separated on Judgment Day, when Sarah would die.
For me, the answer to all these issues of when Judgment Day happens and such is that in the third film, which would end with John sending back Reese and our beloved T2 Terminator, would be that John realizes that he has to send them back, and he has to do so with the info they originally had. The original date for Judgment Day is always a lie. One that has to exist. He would come to believe this thanks to Sarah leaving behind tapes or some sort of notes on her theories.
Then if you want clean air, have movies set after that point, during the war or the aftermath. But they want to keep delaying the war to make these movies and it is dumb.