You can't make another "The Terminator"-movie
Sure, you can make lots and lots of movies, and give all them some kind of name that has the word 'Terminator' in them.
But you can't really do anything about the story of "The Terminator (1984)", because it's an impeccable 'bubble', it's a finished story, with all the interesting and juicy bits already being told.
You can only take the premise and then mold it into something separate, something different, and PERHAPS create something exciting and intense (hasn't happened yet, except maybe the way 'The Matrix (1999)' did it).
And please don't bring up that kids' live-action cartoon with 60% cringe, 20% CGI and 10% watered-down 'don't kill anyone'-non-violence and 10% of 'story' (97% of which was simply copy-pasted from "The Terminator (1984)" and then perverted, mutated, twisted and mutilated until the already established, perfect time-travel paradox was destroyed, so now nothing makes sense).
Doing _THAT_ is not really making another 'The Terminator (1984)', it's more like 'making a bad, kid-appeasing production line copy' of it and failing to make sense.
Really, it's just the SAME story retold, without making any sense. It would make as much sense as if the next movie would just target older and older John Connor with different Terminators... oh, right. They did that, too.
My point is, you can't really make a prequel that would be interesting to anyone. Anything happening before 1984, or even before that faithful week, would just be Sarah's and her roommate's boring, dull, monotonous everyday life. Granted, it would be the glorious eighties, but still.
You can't set it in the future, because we already know from "The Terminator (1984)" everything important about the future, and anything else that happens - OR even showing us how it all happened, wouldn't be interesting, because it'd be just some boring warfare against machines until humans win, or it would destroy everything we imagined every time we listened to Kyle explain the story to the cops. No movie can match imagination, so it's better to never show it. Oh, they did that, too, of course.
So the future is basically just depressing warfare without anything interesting happening, the past is just mundane everyday life of Sarah and her roommate - and the middle part was already shown so perfectly, there's no point in messing with that (though they did that, too!).
There's no organic, natural or even plausible way to insert any new or other story to the original, because it leaves no room for such. Past is boring, present is already perfectly told (and would NOT benefit in adding details), and future is boring outside of what the movie shows and tells us.
It would either just REPEAT everything the movie shows (they did that, too..), or it would just be a completely irrelevat, TACKED-ON sticker that has bad glue, it wouldn't stick (as we've seen).
There is no WAY to make another movie from this story and have it be interesting, the movie's story is just TOO TIGHT, and it's told TOO WELL, and the story is just so COMPLETE - it has clear beginning, middle and end, and everything else exists only to serve the story.
Therefore, you can either DISMANTLE it and build something new (which probably won't be as visionary and great), or you can just USE its elements and try to come up with something different (The Matrix succeeded, so this might work), or you can try to twist, turn, mutilate and add things and change things until you end up with a mess, bad copy that doesn't hold together or make any sense, but hey, at least you get to make the scariest villain robot do GOOFY things when it tries to imitate humans (groan!).
The only way I can see an interesting movie can be made out of 'The Terminator (1984)', that some people stupidly call 'franchise' (when it's really just a vision-based great gem from the 1980s, plus lots of money-based greedy 'sequel attempts' that make no sense), is..
..that you just take elements from the story, but tell a completely unique story that has nothing to do with the original's story or characters or machines, except functionality and looks, perhaps.
The story about 'somewhat sentient robot that's scary and can scan things and people' is always an interesting one, it doesn't have to be "The Terminator" to be exciting, as 'The Matrix' has actually shown us.
So you can't REALLY make 'another' 'The Terminator' movie, it would never have the same excitement, same feel, same energy, same atmosphere, or same, intense performances.
That they still try this, just shows they don't understand what made 'The Terminator (1984)' great. And when masses lap up that cashcow that was the so-called sequel, just proves that massed don't care, so maybe 'Fate' will be a success.
Of course they have to subtitle the movie's name with some cliché line from the movies, because who needs imagination, right?