It’s already changed the culture significantly, of course. It has had a change in what kinds of sex teenagers expect to have, since that’s become a primary source of information on sex for them; but I’m not sure that counts as a cultural change. It’s better addressed in a question like What Is the effect of pornography on young teens? , although there’s curiously few responses there; there are statistics around on that question.
For broader cultural changes, I’ll venture:
- Mainstreaming (to some extent) of porn actors. It’s much easier for porn stars to transition to at least B-grade celebrities, without being stigmatised. There’s still a barrier for “serious thespians”; there was a fuss when the porn films Sibel Kekilli had made were unearthed. (And they weren’t really buried to begin with.) But Sasha Grey hasn’t suffered for it, and has probably gotten a lot further in her non-porn career than, say, Ginger Lynn did.
- Public acknowledgement of porn. Not everywhere in everything; “adult topics” are still curtailed for distribution on Quora, for example. But the open discussion of porn is far different to 30 years ago.
- More skin shown in “mainstream” TV and Hollywood. That’s a broader cultural move in the west, and it has run at different speeds in the US and Europe; but the prevalence of porn has something to do with making it less of a big deal.
- Causal use in the vernacular of obscure sexual references (that porn has made less obscure), particularly in metaphorical or non-literal senses. For example: A unicorn bukkake on a canvas is not art.
- The reinforcement of a laissez-faire attitude towards sexual practices, simply by exposing the diversity of sexual practices that people are into.