Personally I wouldn't mind seeing more of the Future War. I wish Terminator Salvation had been a better film so that we could've gotten two sequels of that, a nice trilogy to cap off the entire franchise.
I'm not going to lie and say I won't be in the theater for Terminator 5 unless they do some atrocious casting or other creative decisions, but that being said, I think they should leave it alone. Going back to the past just seems like a waste to me, especially if its to attack another member of the Connor family. Maybe if a time traveling Terminator had a different mission that would at least make it not so run of the mill.
In any future film it would be great though to get a nod or two to the Sarah Connor show, acknowledging it's part in the overall franchise too.