I think there are probably a couple ways to look at that such that I don't think it would be taxable - or, if it is, there isn't much, if any income.
One, my understanding is that you are simply exchanging your vacation points for reservation points. The points in and of themselves have no value. It is sort of akin to converting credit card points to airline miles through Chase or AmEx. Those points, in and of themselves, don't entitle you to anything specific, but can redeemed for whatever Disney has decided to let you redeem them for.
Two, I think you could say it's part of the terms of your membership you purchased up front and so you've effectively paid up front for this contractual right (granted, it is dependent on whether Disney offers the exchange and they reserve the right not to).
Three, even if there is a taxable exchange and we assign value to the points, you probably get into question about valuation. What is the value of a vacation point and what is the value of reservation point? Probably a pretty good argument that the value of a reservation point is less than the value of a vacation point, in which case, you're actually incurring a taxable loss.
At any rate, much different than the broker swap programs where you agree to rent out enough points to pay for the cost of your cruise and rather than having the rental dollars routed to you to then make payment for the cruise, you simply have the money routed directly to the broker who makes payment on your behalf. It's really just a pure play to avoid the 1099 reporting obligation.