If you put a deposit on a room (not Concierge), that deposit is fully refundable up until the Paid in Full date. Concierge deposits are not refundable.
When a certain percentage of rooms within a category have been reserved the category goes GTY (guaranty). There are still rooms in that category not booked, but
DCL uses them to manipulate the reservations later. Those reservations will receive their room assignment at a later date (anytime between booking date and embarkation date). The cost for a GTY reservation is the same as if you selected a specific room.
Since there's a whole lot of interest in the Hawaii cruises, and a lot of people put 3 day holds on some rooms, it appears that a lot of rooms onboard have been booked. Some of these will open up after the 3 day hold (after people re-think "how much is airfare? Can I get time off work? Take kids out of school?"
Sadly, since so many reservations were made, the prices have increased. Chances are, even if all the 3 day holds cancelled, the price will not go down.
IGT, OGT, VGT are the last minute restricted fares that DCL offers on those cruises that aren't selling well, usually after the Paid in Full date.