Yes have to agree that the bubble will pop. The reason it pops is because the small amount of people who want them all end up with them and then the demand is satisfied. There will not be a massive influx of people born in 1980 onwards who want to relive another generations period of growing up.
The utes will find their value after the vans die down as the ute culture of the 80,s and 90's is relived.
Look at vintage cars from the 1920's to the 1940's. They are of little value now compared to the early 80's.
Time moves on just as it always has.