In my experience when an economy starts to recover and demand increases, prices for desirable used vehicles will also start to rise. I'm not suggesting that they will go back to what they were, but they will increase to some extent.
Regrettably, the Zed is not such a desirable used vehicle or prices would not have collapsed to the extent they have, even with the tax/fuel issue. IMHO the best that can be hoped for is that prices settle and hold for a while. I'll be delighted but gob-smacked if they rise at all.