I'm not so sure the WT will go on for hundreds of years before a split and the reason is that so much is demanded of the rank and file that they barely have time to themselves once work, meetings, and ministry is taken into account.
The organization demands so much and there is nothing about what they do that creates friendships between people at the Hall.
Most churches have some form of community gatherings, even if it's just a meal.
The Watchtower has NOTHING sponsored in the way of community meals, day trips for the elderly, youth groups etc. They have nothing.
People need to feel wanted and part of something. We are, for the most part, social creatures. The Watchtower does not fill the void in people's social lives. That, coupled with "expectation postponed is making the heart sick" is enough to dampen their zeal.
Will they be around in 10 years? Sure, but the quality of witnessing and the meetings is very dumbed down.
They have nothing to look forward to.