Unmolested first gen RX-7s SA & FB values are going the same way the R-100s, RX2,RX3, RX4 , Cosmos and REPUs . A littre bit of a slower rate due to high production numbers , but never the less they have bottomed around 2009 and are have been increasing in value ever since. There are two main factors that are driving the first gen value up in North America.
First there are many enthusiasts that customize and modify their car and run the rotary simply to compete with the muriad of 30 year newer and $30K more expensive street cars & bikes. They often will hammer their car repeatedly with no regards for collectability and will drill, screw, cut and mount almost any speed equipment , necessary or not to remain competetive. When done with these chassis these cars are often only good for a parts donor for another chassis.
The second group driving up value are the racers- Chump, LeMons, Drifters, Sport Tuners, SCCA, IMSA and other clubs racers are gutting and cutting in an alarming rate.
My suggestion for the wise- find a complete barn find & sit on it, you won't be sorry