Reading through some new interview info and Cameron is saying that the first new film will be a direct sequel to T2. So all of the Terminator films that came after it are being dropped down the memory hole.
Concerning some possible plot points Cameron talks about how the flesh component for the T-800 would probably have had a human genetic donor so perhaps Arnolds role will be that of a future war resistance fighter who is captured and used as a template for the T-800's coverings.
Based on that, Linda's role could possibly be future war Sarah who befriends Arnolds character and tries to save him after is captured by the machines.
Cameron also talks about Arnold and Linda passing the mantle to younger actors to carry on the franchise. So, before he is captured, Arnolds character and Sarah mentor the young resistance fighters. And, after Arnold and Sarah are both killed during the rescue mission, the young resistance fighters carry on the war with the machines in films two and three.
Just speculation on my part but this plot line would mean no time travel and no old Arnold as a T-800.