If the tribulations started tomorrow, and all you knew of the Bible was what the JWs had told you, would you suddenly think, "They said this would happen, and it is, therefore they must be right", and go running back?
Or would you think, "just because eventually Biblical prophiesies came to pass that "they" had read you from the Bible, doesnt mean they are the chosen religion, because they get all these other doctrines wrong", and know these doctrines well enough to be able to convince yourselves.
Replies such as "It wont happen cause its a fairy story" wont really help.