Oh the upgrades.
I dont know about DVC, you'll have to call and ask.
However 3 times we have got a free upgrade.
We booked an inside room and got free upgrade about 6 weeks prior to the cruise to botha port hole room and 2 other times to a balcony room.
Sometimes when the lower priced rooms sell out they will move people up to make room at the last minute to try and sell out more rooms.
This only happens when the ship isnt full. Lots of empty rooms tha tneed to be filled. I tmakes sense that to fill the ship they make the lowest priced rooms available for last minute bookings. So those who had them booked can get bumped up to fill the more expensive rooms.
It is just a random thing to happen. No way to just aks and get it, it doesnt happen that way.