hard to say if they will go up or down.
You can pick one up for between 8 - 25 thousand and the price will reflect the car you buy.
For 8 grand u might get something with rough body, no rego, blown engine, and overall BAD condition.
Then on the other end of the scale you might get a car that has a rebuilt RB25DET upgrade with a nice respray, wheels, suspension, stereo, rego, that is in great condition that the previous owner has fussed over and washed every hour on the hour...
The general price range at the moment seems to be from 13-18 thousand and I think that this will remain the same next year.