I think chances are good the WT will be around for a long time. The question is, in what form? It is facing attack on several fronts right now. More likely will follow. Over time that will change the nature of the organization and how it operates.
Many factors play into the situation, including the internet, ex-members and their activities, governments taking action against abuses they see, economic factors, and changes in the publishing business, to name a few. Just like Rome didn't fall in a day or for a single reason, the WT won't either. IMO they are too big, too wealthy, and have been aroung too long to disappear any time soon.
That doesn't bother me though. In fact it may be for the best because many followers won't be in a position to cope successfully with the demise of the WT, and those people have been hurt too much by them already anyway. I don't want to see a bunch of suicides of people who can't face the truth about "the truth".
The WT's existence is not a problem for me. The damage they do to their followers and the greater world community is. That is what needs to change as far as I'm concerned. Over time, that can and hopefully will happen.