I've been thinking about this. I'm a writer, and I've wondered whether it would be possible to get together a good director and good actresses and make a really good porno.
Right now? I think the answer's no. The problem is that you're going for two audiences: the porn-watchers and the content-seekers. The porn-watchers pay for the scene. The more scenes you have, the better. The content-watchers are the ones who'd watch something straight through if it was worth watching. The problem is, a large part of writing-directing is a matter of taste. When you're writing a sex scene into something, you only keep what you absolutely need to advance the plot. Most porn scenes are 10-20 minutes long, which means even if you only have one per film, you're making a really imbalanced product.
I can see writing an interesting, compulsive scene if you've got great characters and great acting, and if you weave plot in. But the more of that you add, the worse the scene gets for the porn-watcher. It's much more a zero-sum game, where you can't win with both at the same time.
And that gets to the bigger problem: porn is not intended to be art. It's meant to soothe people who aren't getting something they should be getting. If you're getting great sex, you don't need porn. You can subsist entirely on art pieces that aren't erotic in that sense. I'd put porn in the same category as something like Office Space in that the main intent isn't artistic merit, it's helping somebody who's in a situation they don't like. The fact that it's no sex versus a dull job doesn't change the fact that neither one is quite as funny if you aren't in that sort of a situation.
(Art nudes, by the way, aren't meant to be erotic. Usually they're meant to capture the human body in its entirety, and there's nothing erotic about the human body unless it's actively teasing you. The novel Syrup has a great scene describing this. Nudes aren't sexy unless you've been teased with a partly-clothed body, and when the girl isn't deliberately denying you the sight of more.)
Now, I can see porn becoming more integrated with movies and TV. I can imagine, in a long-running TV show, a "moment of release" sex scene that literally climaxes seasons of building tension. But that's not the porn industry. That's a little porn added on to a much bigger thing.
Look at how porn is used in books. Pulp writers (Dean Koontz and kin) use it wholesale to raise reader interest during boring sequences. That's pornography in the current sense. Once you hit higher art, though, sex scenes are always used to portray something. You lose the full erotic impact. People aren't buying literature to jerk off: if anything, the jerking is incidental.
And so there lies the problem. Pornography is by its nature a low-brow product. If people pay for more, they'll pay for something that's not inherently pornography. And that means the current porn industry is screwed (ahahaha pun). If you want to masturbate, amateurs are perfectly fine. If you need a level higher, there's always piracy in the form of streaming legal videos, which the porn industry, shady as it is, can't compete with as easily as the RIAA can. They're fighting a battle with everything against them.