I remember Collin Trevawhatever had said he was going to shoot IX in 65mm. Has Abrams kept this decision in place?
Short answer: no.
Longer answer: The first official photo (the only official one so far if I’m not mistaken) from the set was tweeted out by JJ himself back in early August the day they started principal photography. It very clearly shows a Panavison 35mm film camera, one of the very same used to shoot TFA in fact (it has “VII” and “IX” etched into the side in the yellow wireframe font). In the photo you can even see the lcd display viewfinder which shows that the camera’s capturing a native 2.35:1 image just like the majority of TFA and TLJ.
So, they definitely won’t be shooting the whole movie in 65mm judging by the photo, probably not even the majority. Abrams shot the escape from Jakku scene in TFA entirely in Imax, with the picture filling the screen if you saw the movie in that format. Johnson shot some Imax for the Ahch-To scenes and some taller aspect ratio stuff for Krayt (it’s unclear if this was also actual Imax or some other format) but opted in the end to keep the Imax version 2.35:1 throughout the entire movie just like the normal version.
I’m sure Abrams will probably shoot some of IX in Imax as well, although there hasn’t been any official word AFAIK. He may even mix in some 5-perf 65mm stuff as well (that’s the normal 65mm Trevorrow wanted to shoot all of IX in).