I could see the value for most of them falling. Here's my thoughts on this matter. With the advent and the pushing by most in society that gasoline/diesel engines are old,dirty, and unhealthy for people and the environment plus the push for electric vehicles, I think only a few will hold value or some value but, I could see them becoming just art pieces eventually due to these circumstances and people not wanting to work on them minus the select few. Myself personally, I have what I have for personal enjoyment and value.