As to taxable I would check with an accountant. As to some other issues:
Disney could not make changes in the future as to the rights you already have to rent. However, Disney already does have a vague limitation in the disclosure documents you received as to renting in that renting for commercial purposes is prohibited and that repeated renting can be considered a commercial purpose. Thus, Disney would not need to change the rights you have, it would only need to exercise the limitation it placed on those rights at the time of sale to you. Basically, Disney does not desire that people buy simply for the purpose of going into the business of renting points and that is likely the reason for the limitation. Where do you cross the line between (a) being an owner who rents occassionly or rents out some points to cover dues and make a little money but mainly has points for personal use, and (b) being in the business of renting is not clear. Disney's vague limitations may have something to do with vague statutory terms in Florida which require someone "in the business" of renting hotel and resort property to charge the Florida and county rental taxes (11% to 12% in WDW) and submit such to government authorities; in other words there is some point, not clearly defined, where you could be considered to be in the business of renting and thus must charge those rental taxes or possibly face fines or other penalties.