Bemused, I just checked the decline of numbers of church-goers in England, Wales and Northern Ireland. Ten years ago the numbers were 6.3% with a projection of 4% by 2020. The average age being in the mid-fifties. (I would have thought older). Two thirds of British people are not affiliated to any religion and less than 20% nominally and historically associated with the Cof E.
It is my expectation that JWs will decline in accord with the general avoidance of religion here. nevertheless there will always be a rump of desperadoes who cling tightly to their religious hope even if or when the Watchtower org collapses. It is the blind possesion of hope which triumphs over reason. The same for the numbers of those who believe Jesus to be coming... whether on clouds or apparent to all (it is highly ambiguous), the concept must sound more like a foolish fairy-tale to the more literate and educated people of today's world.