Stronger $AU means cheaper importation which means cheaper prices on resale from both the cars coming in and the cars already here.
However, the primary problem with import resale is basic supply and demand. There were so many skylines and like vehicles imported pre the 89 ruling that they are now effectively a dime a dozen and nothing will change that. The price will level, but not rise and once they get older it will just continue to fall. Not to mention with the new P plate laws, the price will continue to fall as the next generation of teenagers realise they can't buy a skyline which, like it or not, accounts for much or at least some of the skyline market. Unfortunately for sellers the days of 20k r33's are well and truly gone, good for buyers though.