Sanatana Dharma can not be destroyed. It has always existed and always will exist IMHO. It man be manifested, hidden or misrepresented, can it not?
Yes, of course, but that's all in the maya, outer realms of the intellect, not the inner soul nature. It's nature is intrinsic, hidden within the DNA structure of man. So it there is destruction, it's temporal. We have no messiahs of the past or future.