Would depend which way the pendulum ends up swinging afa "sex positivity" vs. puritanism in modern feminism, plus of course how mainstream porn develops. Looks to me like it's ending up equally or even more compartmentalized, just for very different reasons.
I mean current moves are more along the lines of dropping topless women from tabloids/Playboy ending nudity, Britain trying to age-limit porn, etc.
Also probably comes down to the basic technical difficulty of targeting ads on websites often browsed in private mode. Which will probably keep being the case for a lot of people, for practical reasons, regardless of how normalized porn might be.
In fact, as this generation of baby boomers dies off, I have a strong feeling porn will become far more normalized and have more prestigious non-porn brands associated with it, so long as more prestigious porn brands can rise up.