The only way I could see doing this is maybe figuring out some way to offer them to DVC members... but even then I don't see any way it'd be financially feasible for them.
I think the basic idea would be something similar to when a company first goes public, starts selling stock. That infusion of money coming in from the stock, or in this case, the lifetime pass, would be used for other investments that would generate more revenue in other ways that would offset the fact that the purchaser would never pay for admission again.
Plus, you deal with the possibility/probability that, but never having to pay for admission again, many lifetime passholders will spend more money other ways, more expensive resort rooms (at full pop, unlike those jerks with annual passes
), appetizers AND desserts with every meal, and of course, sooooooooo many more souveneirs.
Finally, there'd be a strong possibility that the sorts of people who buy lifetime passes would then go on and buy lifetime passes for relatives or their kids, who would then grow up to do the same. So the checks keep coming in.
What I'd suspect is that this is a rumor that pops up whenever there's a downturn (or expected downturn) in tourism - a "limited time offer" that provides WDW an extra infusion of cash to offset the lean times, then when things start getting better, the offer expires. I'd be tempted to get one too if the price was do-able. At the very least, some idea of a multi-year pass that people can buy on the odd occassion that they have a chuck of change to "invest" in future vacations.