Sometimes you can get upgraded, but it really depends on occupancy, whose leaving when, whose coming in when, etc. I can assure you that these are NOT as easy to come by as in the past. One on hand, it is because people have abused it- for instance, booked one standard room and one waterview room and demanded to have the standard upgraded for free, or more commonly "I always book a standard and I always get upgraded, I want an upgrade NOW." On the more litigous side, due to things like Enron, Worldcom, etc. "free" upgrades for no real reason can raise eyebrows in during auditing...there must be a significant reason (hotel sold out, guarenteed connecting but all taken in that room category, etc) to do an upgrade nowadays. A company like Disney always has a target on their back, and they need to be careful.
If you do want to ask, do it tactfully (something like "is there a better view available?" or "is there a possibility of upgrading to a better view?" could always open things up without being overbearing) and be prepared that you may be asked to pay....if you are nice and casual about it, you may not be and that would be great!