No, hotel rates don't work that way. Hotels publish a 'rack rate', the per-night standard rate for the room, and then they may or may not discount the rate from there.
Disney's discounts and promotions are generally offered well in advance. They will usually only discount the resorts and room types that aren't booking to their satisfaction, and the promotion will usually only be offered if you book by a certain date. Once the dates are up, or all of the discounted rooms are booked, the discount is no longer available.
So, it's possible that if you book very close to your vacation, you may find few or no discounts available, but you'll never pay more than the rack rate (plus taxes).
