You are guaranteed that category or better (anywhere on the ship). I've heard that upgrading is based on the following...how early you booked your cruise, how much sales your travel agency has done w/that cruise line and other factors that we may not know. You would think that if all cabins in your chosen category are sold out that your chances to be upgraded would be favorable. The cruise lines bump up from the category to free up least expensive cabins because they know they can sell those cabins better than the more expensive cabins. It all depends on how well that sailing is selling. If its really popular cruise/itinerary and they know they will sell out then you may have a problem getting upgraded. But if that sailing is selling slow then they will upgrade to free up the least expensive cabins because they are easier to sell. Hope this help and good luck!