There was a 50 year gap between the failed dates of 1925 and 1975.
Memories fade, people die, and who cares what was said 50 years ago.
Most JW's now in the religion werent there when 1975 was a thing. Even my mother who was baptized in 1974 who I do remember speaking about it back in the day, can barely remember what the fuss was about. For active JW's who are doing all there studying online now, its practically impossible to find any WT contemporary reference to 1975.
i read recently (sorry I cant source it right now) that at the time, even Watchtower may have taken the view that even if they knew 1975 was wrong, the short term gains would far outstrip those who left leading to an overall net gain so it was a risk worth taking. I have been doing a bit of research lately into the 1975 prediction, and there is no doubt it spurred on activity and was a massive shot in the arm to WT at the time.
So... nearly 50 years on after 1975, do you think they would try it again. Short term boost in numbers, get them in and captive, those that woudl leave arent worth having anyway?