For Centuries what kept our Jewish friends going was Prayer , and the idea expressed within their prayers, and actually expressed, after meals if I remember correctly, " Next year, in Jerusalem".
I guess a similar long term view will keep the old stalwart JW's going for a while. But the younger ones who have never really bought in to all of the nonsense will continue to drift away, I think too that there will be a general idea across the World that we should not go back entirely to what we used to call "normal", and some kind of reset may have to occur within the JW Org to go along with the Zeitgeist.
It is obvious that a 19th Century Apocalyptic Religion is well passed its sell by date, so they are going to have to use new Marketing of some sort, or die quickly as an Org. They have tried the re-branding, the On-line Web based stuff, the Carts etc and they did not improve the gaining of Converts, so something else will have to be tried. Crying Wolf for 150 years is looking increasingly very silly.
There is speculation that they may try a reset of Date to 2034, to keep the fear of "The End" going, that will only buy them a little over a decade, so will be the final time for such a move. I would think their advisors would warn them off from such a short sighted move.