I think there is room for new ones and i would do it with the right partner/s and exclusive content access.
My idea of the good sponsor i would like to release one day is one who could release some paysites with exclusive content and with a dedicated studio and models so we wouldn't run out of quality content after the first couple of months as lots of paysites do. I have funds, traffic, contacts and experience on affiliates management but i miss the content part, i guess my perfect partner would be a studio owner... but probably that would be the dream partner for everybody
To run and specially to start a sponsor program is a really hard job. I owned a dialer sponsor a few years ago for the Spanish market and it can really waste you, but at same time i enjoyed it a lot and made good money, until the dialers biz became shit with all the cheats, exploits etc and i moved to the international business.