Like AK has said, the WTS has material assets that it can liquidate, reinvest, and perpetuate itself for a long time. To think otherwise is either ignorant or naive. It is also built upon a symbiotic/parasitic relationship between its leadership and members, (as any authoritarian system), and as such, this cycle is difficult to break. By all measures, the WTS will be here a while. Religions have never proven to die easily.
Having said that, I do think in the social sense a tipping point has either been reached, or is just about to. Many long standing institutions have been threatened by the free availability of information and the better educated society that has been made possible by the offering of that information. Ten years ago people would have thought gay marriage, legalized marijuana, improved US diplomatic relations with Cuba, removal of "don't ask don't tell" in the military, etc., to be impossible. All of these things happened, seemingly overnight. By the same measure, when I left the organization 10 years ago, the WTS was anti-internet, never would have allowed social events at a KH, did not beg for money, had no singing carts, no masturbation videos, no televangelism, etc., etc. While in the case of the WT, none of this progress in of itself, it still represents a response to changes in society the WT never thought it would have to adjust to. That is a good indicator of how threatened the WTS actually feels by a changing society around them. The more they change, they less stable they become, since almost all of the changes are tactical responses to either real or perceived threats, not long-term strategic moves.
I'll be long dead by then, but I doubt very highly the WTS will be here by the 22nd century. In the meantime, they are appealing less and less to "normal" people all the time.
d4g