Upgrades may be given to those booking on
DVC points, points/cash combo or strictly cash non DVC. That being said, upgrades are very few and far between. We do hear of them (as shown by the posters above) here, but for every one we hear of, there are hundreds or thousands more that did not get upgraded.
That being said, one can always hope. However, be sure you are happy with the category you book for your cruise. Otherwise, you may end up miserable that you never got a "free upgrade".
In my 13 Disney cruises, I was upgraded complimentary only once. And I had booked that through a
travel agent (not DVC).