This is a commonality shared with a number of other cults - the quasi-secret belief that is too weird or terrible to speak of openly in public.
If you ask a JW who comes to your door if only JWs will be saved through the end, they will provide you with a better "um-uh-well---that is above my pay scale - ehhh, um" than did Barak Obama in that church debate. You will not get a simple yes or no - unless of course the witness in question is one of the sub-one-percentile of really really hard-core meanies. Normally they will not even reveal this until a new convert is well along with "bible study" and closing the corner into baptism.
It is the JW equivalent of the Mormon holy underwear, the secret suicide pact of the Peoples Temple, the story of Xenu and the aliens for a 6th level Scientologist, the secret legends of Hiram the Architect for Freemasons, and so forth.
There is a good reason such things are kept secret: The simple fact is that they are too silly, repugnant, or creepy to reveal to a normal thinking person until a good deal of indoctrination/brainwashing has already set in. The Scientologists even teach that a non-devotee might be driven mad by the higher levels unless they have been carefully "prepared". So with the witnesses and their real belief of Armageddon.
While most of these little secret rites may seem just a little silly, or perhaps embarassingly bizarre...the teaching that the God you worship is soon going to come and kill every man, woman, and child on earth (except for the cult members in good standing) is a startling revelation of intellectual immorality of the most insane depravity imaginable.