In case of a natural disasater, my feeling is that DVC would do their best to make things right and would try to accomodate members at other DVC resorts. I think the "legalese" allows them to just let us receive our insurance payments if the resort could not be rebuilt. In any case, I think they would be fair to members. I don't think we'd be able to participate in the non-Disney properties because, as was already said, there would be nothing for DVC to "trade" to pay for the stays.
If the destruction were caused by a bomb wiping out WDW --- then hell, we've got a lot more problems to worry about than using our timeshare. I hope never to see anything as devastating as 9/11 occur on U.S. soil in my lifetime.