The Governing Body will not actually instruct the "Witnesses" to preach a message of doom ,it is one of those things that is going to happen in the "near future" keeping the flock in expectation of what`s going to occur .
However it will never happen for the very reason doing so puts an end time line on their religion .
But then again having said that they did publish in the 1970`s ? "Babylon The Great has Fallen Gods Kingdom Rules " and saying that false religion, Christendom and non Christian religions , has had its day and was being abandoned by the masses since 1919 ?
Yet their is no evidence of that today in 2018 is there.
Muslims have over 1 Billion members and still growing
Catholics are over 1 Billion members
Protestants are over 1 Billion members
Non Christian religions would have to be in the Billions ? surely
So even if they did start preaching a message of doom it would go the same way of all of their other many failed predictions they have made in their 100+ history