Porn is a big industry, and just like gambling tied to bitcoin in the beginning, it will be perfectly normal that porn will attempt to do the same now. The relation wont just be with bitcoin. In fact I think it will be much easier to relate porn with ethereum (with the creation of ICOs), and with coins that offer more privacy than bitcoin (like monero). New projects are created in the ethereum network, to allow users to create content and don't be "robbed" by the middle man. This looks like a great setup for porn webcams for example.