If it helps you sleep better, the "black box" analogy isn't that great. ACM'* only start recording when the car decides that the airbags should be deployed; then, a bunch of data
gets written to the ACM'* write-once memory until it fills up in 5-10 seconds.
This article talks about the legal aspects of the module and your data.
It'* long, but apparently more interesting than sleep.
As far as OBD-3, there seem to be many more conspiracy theories and decade-old chatter than actual facts or proposals. I think that as long as the manufacturers don't have trouble shoehorning new features into OBD-II, CAN, and OnStar; and that doesn't affect the states' ability to read the emissions data, there won't be an impetus to replace OBD-II anytime soon.