It seems to me that with the way the economy is going right now, there is no way to determine trends in even specific timeshare values. Folks of every income level are losing jobs and/or asset values every day. Some are making no moves, others are unloading everything they own, others can be anywhere in between those extremes. The guy who lost his job three months ago may have just unloaded his SurfWatch unit for a song, but the guy who picked it up got himself a steal and is probably anticipating an equity return when the market rebounds.
The only certainty appears to be, a single week's value is whatever offer has been made on it today. It's all way too uncertain for me to do anything but sit and watch and hope.