This part of the porn industry has changed so fast in 10 years, anyone who thinks it won't in the next year is a moron.
Firstly you have to know what the TGP market is. Surfers who will never pay, surfers who cannot pay, surfers who sometimes pay and surfers who use it as a sampling medium to find the next site they will belong to.
Never pay, forget about him. he will probably become a webmaster.
Cannot pay, too young and busy getting hooked to porn.
Sometimes & samplers, these are the guys we earn our money from and probably why The Hun can charge $500 a day.
What might happen is the paysites will realise that a $500 a day banner is cheaper and a lot less trouble than keeping, finding and giving webmasters a slice and making sure they are not screwing you rotten.
Plus the good TGP sites will realise that they could get $5 a day a listing for the lower listing for the first week and then some of the clowns will disappear. Some can't afford to buy a $5 set to work with, let alone $5 a day to list it on a single TGP.
Let's be honest, other than providing free porn for those who are unable to pay at present TGPs do not create traffic, they merely guide it. So if half the crap webmasters and TGP sites disappeared tomorrow would we lose a single surfer?
This is just my opinion but the market will change and change fast, that you can be sure of.