Yep, it's gonna happen. And since WA is the last state in this country to ban detectors, there is no further local market to on-sell them to. So, unfortunately you ppl with those $800+ detectors will either run a big risk of being stopped by the plods when they have their radar detector-detectors trained on you, or you could quickly find some sap who hasn't heard the news & flog it off on the cheap.
Oh, and unlike the firearms buy-back of years ago, there will be no "detector buy-back". Sorry folks