If it forces down valuation of expensive cars after 3 years there are going to be a lot of bargains around for those with cash. More likely a large trade in second hand cars being shipped to third world countries will get under way. The Japanese have been doing it for years because rules make it difficult to keep vehicles more than 5 years old. As I recently found out it costs more to keep my 12 year old Alfa on the road than it is worth and even if I kept it I risked not being able to use it in months of high polution levels. It would be banned for the centre of Milan all year round and during winter was banned in several regional areas.