i am trying to figure that out myself. i played the dlc, and am mostly to lvl74.
my op8 gear dropped a rank somewhere there. my guess is that it becomes lvl 80 gear when you hit 80 (it’s the same damage etc).
but this leaves the question is op now 81 to 90? (ack)
So yes, as you level up Op gear is relabeled as lvl72+opLvL, this means when you hit 80, all your gear if it was op8 is also lvl 80.
This makes sense as the level cap has risen, so the op level starts accordingly. If a toon is op8, they have the ability to carry lvl 80 gear but not the skill points or health. But this does imply that digistruct peak might very well go up to 88 (or 90 if the article I read says there are two more op levels now).