Sent an email to Powerplay a few months ago as I'll be looking to purchase one around the end of this year.
I asked them if they think R34 GT-R prices are going to drop any further and they replied with this:
Hi Alan,
It is impossible to predict what will happen with R34 GTR prices in the future, at this stage the prices for good condition, low kilometre cars are remaining firm.
The release of the R35 GTR will definately have an impact on R34 GTR prices & I will be closely monitoring the market over the next 3 months. I think the prices could go either way, up or down. If the R35 GTR sells extremely well there will be a lot more R34 GTR's available as owners upgrade to the new model. But, this could push the prices of the R34 GTR up as overseas markets compete with each other. Also, there is the local Japanese market to consider, R32/33 GTR owners upgrading to the R34 GTR, this will also push prices up.
As more GTR's come on the market you would expect the prices to drop but demand from overseas buyers competing with the local Japanese market could keep the prices at their current level or higher.
Being the last of the RB Series, the R34 GTR could very well become an icon like the R32 GTR where a very good condition R32 GTR can still cost up to 4 million yen. Only time will tell I suppose.
Kind regards
Jo-Ann