Keep in mind that just because it's listed in II, it doesn't mean it would be easy to get or not.
First, someone owning there has to trade out. To those owners it's a lot like we
DVC owners. We bought to stay at DVC, not to trade out. Likewise they paid big bucks for their timeshare. Most likely they paid more for that than any of us paid for an equivalent 7-days at DVC.
Second, if someone does trade out, other Marriott owners get first pick at the resort.
Third, if it finally goes out for general trade, then DVC is one step up as being a better trade so in this case we'd have a better chance than someone owning some other non-Marriott resort. I would recon the competition would be more between DVC, Hilton, Hyatt etc, as to who got the reservation.
Also, as Diane mentioned, it's all red season, but not all red is equal. Don't even think about the possibility of getting a week for example at Christmas.