Beware of the hoax which claims that all your posts can become public tomorrow, it is just another hoax which is circulating Facebook. There is no reason to be worried about your posts going public by a Facebook action.
The source of the All your posts can become public tomorrow hoax is unknown, and there is no damage which can be caused by this hoax. It is only trying to get people scared about posting information on public.
The All your posts can become public tomorrow hoax
If you see someone sharing this hoax, then simply inform them that it is fake and that it would be better for them to delete the fake post from their Facebook page.