Disney owns a percentage of all DVC buildings. If there are any available for cash they should be available now.. The timeshare has little to do with this unless owners of that DVC transfer the points out in which case Disney can open them up at any time but will do so when it is mots profitable to them being no set date is involved... The timeshare part is owned the owners of the timeshare and it is use or loose-- in other words if a room is vacant an owner looses the money or use of the points and Disney can not sell that room as they do not own it... DVC and Disney resorts are two different owners or companies but yes all owned by Disney.
DVC rental would be your best option but beware that September to January is very popular for DVC crowd and if Food & Wine is still going on it will likely be very difficult to rent at Beach Club. I've been intermittently following the DVC forums here but don't own and it seems that Beach Club during Food & Wine goes first thing in the morning 11 months out.
I would start checking at 11 months out. I've been poking around for our trip for late August 2019 and noticed villas at both BWV and BCV are now available through WDW for my dates.
DVC member rooms for points are kept separate from rooms available for cash through Disney. The only time points rooms can become available for cash is if they are unreserved at 60 days out. DVC members do not own all the rooms, so some are available for cash earlier.