The big "upgrades that everybody makes a fuss about are inside to a suite. The chances are probably like 1 in 100,000. Inside to a balcony maybe 1 in 10,000. Inside to outside 1 in 5,000. If the sailing is a high demand date and the ship is full then its 0 in 0.
Guessing that 4,999 out of 5,000 "upgrades" are from lowest deck to a higher deck, same cabin type. And when you get moved up a deck or two, it will be to the lowest demand cabins on the new deck. All the way forward or all the way aft or right by an elevator. To me those are all perfectly good cabins but they sell slowest because people have conceptions against them.
The numbers above are just guesses. Actual personal results are 40 cruises, 3 "upgrades"
2 of those of the same cabin, higher deck type "upgrades" [one all the way forward and one right by the elevator] and one "real" upgrade, inside to outside cabin. [right by the elevator]
Be very happy with the cabin type you booked, if you're not ready to cruise in that type cabin, you shouldn't have booked it. If you booked a guarantee with the hope for the best but the expectations of the worst and will be happy with whatever you get. fine, that's the only way to look at it.
Dan