Originally Posted by felix_the_cat
Generally guarantees are less than picking a cabin.
Picking a cabin by number does not eliminate the chance of getting an upgrade unless you have told them you don't want an upgrade.
However it does make your chances of being upgraded MUCH lower. Specific cabins are rarely upgraded.
Something relatively new for people with specific cabins booked is the "Upsell". I know NCL and Carnival do this quite often. They will call you with a "deal" to upgrade to a higher category for a price. Often these are decent rates and nice upgrades. Sometimes they aren't any better than the current pricing.