Predicting the future is always a shady business. Part of the reason Watchtower has done so much damage is because it insists on foretelling future events and uses its predictions as an instrument of fear and control, so I am hesitant to follow down that path.
I personally doubt that Watchtower will ever completely evaporate. It will always be around in some form or other. Heck, if there can still be Bible Students nearly 100 years after Russell died then why shouldn't there still be people who venerate the Governing Body 100 years from now? The question is, how many of such ones will there be? Millions, or just a few hundred lunatics?
What is beyond doubt is that Watchtower has started downsizing. The closure or "merging" of branches together with the reduced magazine printing commitments is clear evidence of this. There is absolutely no reason for an organization with Watchtower's religious/world-conquering aspirations to shut down branches and print less literature unless something is seriously wrong.
Whether this downsizing will end up having any impact on publisher numbers remains to be seen. There are early signs that publisher growth is flatlining, especially when you take global population growth into consideration. However, who's to say some unforeseen development won't cause another spike in numbers?
I personally think Watchtower's days as a multi-national corporation are numbered and the rot has already begun, even if it will always be around in some form. I guess only time will tell.
Cedars