Unless aliens come down and say Jehovah is dead. Or there really is a Armageddon were they die off just like everyone else, I afraid they are not going away. Why? Because of sex.
There is one thing that puts more people in religions than anything else on the planet and that is sex! As long as Catholics are having sex with Catholics, Muslims with Muslims and Jehovah’s Witnesses are having sex with other Jehovah’s Witnesses their numbers will continue to grow. Yes, good old sex has created more religious people on this planet than anything else.