I agree that there will be a very gradual descent into almost nothingness.
See what happened with the original russelites - the Bible Students movement. After more than one century past the 1914/15 Russel prophecy debacle and the death of its founder, and no "new light" (that I know of) has been published since 1916, there are still splinter groups that separated from the Watchtower that are still active. It's reduced to almost nothing, but they have somehow survived. They are true believers.
The Watchtower / JW.org will carry on existing, maybe will go through a few metamorphoses. It won't crash and burn. It will just fade, slowly, with a couple of spikes here and there, as they stirr the scarecrow of 'imminent Armageddon', but it will surely fade into utter irrelevance, probably outliving every single one of us here in this forum. In the meantime, it will suffer cuts and blows, financial loss, opposition, loss of credibility, scandals, maybe even a secession or two, etc, but it will carry on, each time downsizing and poorer. I am certain that the COVID-19 crisis will speed up (and be the excuse to justify) some dramatic downsizing moves that we will see soon. But the true believers, ah, those will keep on believing.
And I guess that's the best we can expect about it.