Bitcoin doesn't need sex to sell, it sells itself. That being said, I do think the sex industry could really benefit from bitcoin. I think it's only a matter of time before they get involved.
What if the Bitcoin-payment processors refuse to cater to the porn websites? I have heard that the Bitpay has turned down a number of requests from porn websites, along with similar requests from merchants dealing with legal Marijuana (in Colorado) and those dealing with pharmaceuticals. We need more and more payment processors, as currently Bitpay and Coinbase are monopolizing the market.