Well. One thing for sure - subscription model won't work. It works only for AAA titles, others are gradually shifting to micropayments / microtransactions. (Yes, talk about buying an exp points and "money rules". It works, however, for both parties involved - players and devs/prods/publishmen).
As for sunk costs - terms can be discussed , venture capital can be found, even now, if they're having idea and half-assed implementation - they'll get funding to replace facebook ties (what are they, anyway ? authorization ? storage ? publishing ? ) with solutions of their own, then - marketing campaign and true profit in a year or two. They'll lose independence in the process, but that's the price.