I've seen religions fall before. People still hang on. Hell, there are still Bible Students that follow Russell. So *IF* the Watchtower does fall, there will be believers for a long time, IMO.
But I believe it will fall. Even *IF* it has real estate holdings, you need cash to operate. What do you do? Sell off your Kingdom Halls? Then where do the affected members go? And when that money's gone, then what? Sell more? Once you've sold off all of your Kingdom Halls, then what? Have the congregations reserve a set of picnic tables in a local park? Back to meeting in homes? Back to meeting in homes is where I see it going to eventually and hanging on there for a LONG time. Until a generation or two dies off.
There's the attitudes against college. So you end up with all of these low-income members who can't contribute because most of their income goes to the basics of living. Not to mention it's popularity in third world countries that also don't contribute much.
You've also got doctrine that's killing the religion. 1914? Really? Jesus came over 100 years ago? But he's invisible you say? And you're going to stick with that? But he's going to come back visibly real soon. Real soon. Any minute now. As decade after decade passes. Covering for pedophiles, shunning, etc.
Plus, you have the internet exposing the lies not only of JWs, but of religion in general which is hurting all religions. The category, according to Pew research, of no religion in particular is the fastest growing. Which not only includes atheists, but religious, just not part of a religion. At some point, there will be a tipping point. The more non-religious there are, the less of a stigma it is and the more likely you are to look into it. And it very well could accelerate exponentially.