I think it's important to remember that even if this reservation is long term, once parks open to capacity, there's no reason to worry that you won't get the exact park reservation you want on the day you want it, unless it's like Christmas or New Years Eve. When you show up on any given day, 360 days of the year they are nowhere near capacity and you never worry that you might not get in when you show up to the gate. Why would you suddenly worry the park you want is not going to be available because it will have hit capacity 60 days out? This will just be a way for them to know which park you plan on going to which day, and just like you can modify fastpasses day of if you want, I'm sure you'll be able to do the same for which resort you plan on going to, especially true I'd think if you are Platinum/Gold AP or Resort guest as Remy has hinted at.