I'm not sure whether or not a person would have been disfellowshipped in the late 60's and 70's for saying Armageddon wouldn't arrive in that century. But I do know for SURE that he would have been hauled in the back room and told never to say such a thing again. And if he did, he positively would have been DFed as at that point he would be considered rebellious and insubordinate. Apostacy would not have to enter the picture at this point. Once the Elders tell a person to stop doing something, ANYTHING (right or wrong) he must stop or he positively WILL be DFed.
To illistrate the furvor leading up to 1975: My husband built a home for us in '73. He was told he was not exemplary and could not be appointed a servant because he was not living like the "End" was imminant. In the late 70's he built another house for us that was bigger and better than the 1st. This time however, it was ok since 75 had come and gone, he was appointed an Elder. The "Holy Spirit must have changed it's mind. LOL