They lost a large proportion of followers in the early-to-mid 1920s, thanks to Rutherford publishing end-times predictions so frequently. It was something like 65% of the following, which splintered off into other groups (some of which remain active today, if I am not mistaken). But they managed to recover and grow.
Whether they can do it now, it's hard to say. Rutherford was the leader of the organization during his term, a sort of one-man FDS. So he could make changes more quickly and efficiently (granted, this was one reason why things went downhill at the start of his term). Also, there wasn't an internet where critics could reach a massive audience and virtually "confront" Rutherford and make a response necessary.
I think that the current GB may feel safe, now that they have the '2075 teaching.' They can keep the current ideas going until they pass away, and if the effect on the organization is disastrous, they won't be around to deal with it. Let the next group of GB members try to patch the hull of the sinking ship.