Summarized: free porn will win.
Not summarized:
At the moment, the traditional online porn industry is losing the fight against the web 2.0 version. There's no denying it - just take a quick look at the Alexa top 1000. Sure, many people in the traditional industry will continue to make great money for years to come, but the "pay to watch" model is doomed in the long run - even if hell freezes over and we defeat those who use content illegally.
Not too long from now, more people and businesses will start figuring out that buying content and distributing it for free is a viable model. Create a youtube-like site, only put full scenes on it, support it with ads and upsells (eg, selling downloadable hd versions), and you're in business.
There is no possible way for the traditional model to compete with that. Sure, certain specific content that isn't available anywhere else will continue to sell, but most of the generic porn sites are doomed.
There are only two things that can prevent this from happening: the end of net neutrality, and worldwide government intervention.
The end of net neutrality could possibly lead to an increase in bandwidth prices, which would give paid porn an edge again. Could, though - there certainly is no guarantee that it will go down that way.
Government intervention is actually likelier. A business model like this would clearly give anyone, regardless of age, even more access to free porn than before. That could upset quite a few people, and could possibly be a reason for governments to tighten the laws, or even to block foreign porn sites which give free access to porn.
The way it looks now, though, the age of the paysite is nearing its end.
