Also, be aware that an upgrade is virtually impossible if you have kids -- they tend to upgrade single travelers and couples if it can help them arrange blocks of rooms for other groups or meet other requests. People who normally stay in only Moderates might be offered a discounted upgrade to a deluxe (like Wilderness Lodge or The Polynesian) if the moderate they normally stay at is sold out, or if they have blocked off a building at the resort (French Quarter used to be the best for this -- at off-peak times they would close off Buildings 6 and 7 entirely and offer an upgrade to WL or Poly)...
You should also be aware that upgrades at some of the resorts might NOT be what you want...if you prefer to be close to the main building at Riverside, for example, an "upgrade" might put you in a building twice as far away as the building you normally request to stay in.
I always travel by myself, and go 4-5 times a year. I always stay at POFQ. I have been upgraded to river view rooms I would say at least half of the time. I have been offered upgrades to Wilderness Lodge at the same rate as POFQ on two occasions over the past 5 years. I never ask for upgrades, they are just assigned.