I'm not so sure they'll do too much at the box office to be honest Ken. The last Terminator was a flop, Independence Day, Men In Black, Transformers... All flops.
There's no such thing as a sure thing, unless it has Star Wars, Pixar or Marvel in the title.
There is absolutely an argument for quitting while you are ahead.
It speaks to the law of diminishing returns that the franchises mentioned have each lost more with each successive follow-up - clearly the evidence is outweighed by the Holywood view that more means more, even when it clearly does not.