An opt-out system means that anyone (not limited to Falun Gong and other cults) who is already dead will potentially have their organs harvested except if they registered in a national opt-out registry while they were alive. Organs will then be in such abundance that no one will have to be killed for them as they are now. This will be at no cost to the living. It requires a cultural shift.
It's unlikely that the supply-demand ratio of organs will be balanced anytime soon, or if ever we will have greater supply than demand. An organ donation registry works only if there is governmental support for maintaining and respecting the wishes of those that sign-up in the registry, whether opting out or opting in. In China's case, the government has time and again shown disregard for the rights and wishes of dissidents and those that the party classifies as threat. And as such, there is slim hope of any respect shown towards their wishes and decisions. So, I am not really sure such a system will solve anything. At least till the time the Government stance remains as it is today.
The problems of insufficient donors and that of oppression by the government are different problems. An opt-out registry solves the problem of insufficient donors. As for the government, it will find other ways to oppress people so long as the people don't carry weapons to defend themselves.
