rated R

Good writing, that's what matters

More confirmation
https://variety.com/2019/film/news/terminator-dark-fate-will-definitely-be-r-rated-tim-miller-reveals-at-comic-con-1203272069

Arnold talks R rating
https://bloody-disgusting.com/movie/3573779/crazy-new-terminator-dark-fate-footage-plus-arnold-schwarzenegger-goes-off-pg-13-sequels/

“I am so delighted,” he injected. “I was sick and tired with the last time, when the studio decided to make it a PG-13 rating just because they thought there more dollars in there. I said, ‘Guys you’re so stupid…this is a story that is written and a franchise that is done and written for an R-rating and not Terminator the babysitter type of thing.

“That’s not Terminator, it’s cheating it’s greedy and trying to make more money,” he added with fierce passion. “You have to be organic about this stuff. This is going to be an R-rated movie. I wouldn’t be sitting here today if it weren’t.

“I was so angry about them trying to cut out the blood and gore. In this movie, we have the gore we have the blood – I’m not even going to talk about what I do in this movie – Gabriel literally cuts people to shreds. There’s blood, there’s gore, there’s guts, you can see the heart being ripped out.”

I guess it will be 15 in uk (most recent R rated SF stuff is 15 - BR2049, Alien Covenant, Fury Road, Logan, IT etc) back in the 80s/90s R rated movies regularly got 18 in uk but it has to be very extreme to get an 18 now (last year Halloween got it and Once Upon A Time in Hollywood has been rated 18 like most of Tarantinos)

it'll be the first non 12A rated Terminator since T2! (T1 was 18, T2 was 15, T3 was a 12 even though it was rated R which must be the only time that's happened as R is always either 15 or 18 in uk with PG13 being equivalent to 12A or in some cases 15)

Cameron talks abit about the rating
https://deadline.com/2019/08/terminator-dark-fate-james-cameron-on-re-wired-franchise-possible-new-trilogy-1202707063/

Its official
https://www.filmratings.com/Search?filmTitle=Terminator%3A+Dark+Fate&x=0&y=0