From everything I read

It seems like F.M. Radio will be going away in the near future. I currently have a mint Mac tuner that I don't use but it looks nice on the rack. If F.M. Radio does go away as expected do you think the value of this piece will drop like a rock? The only thing the piece has going for it is that it's a vintage Mac piece and there seems to always be a market for vintage Mac gear.  On the other hand if it can't be used will people still want it?

I imagine that F.M. radio will eventually crawl under a rock and die,but this will not happen within most of our lifetimes. When that death does happen it will be self inflicted and welcome, as 90% of commercial radio deserves this fate. The saving grace of the F.M. is still the non-commercial and institutional sponsored stations that offer a welcome alternative to commercial stations.For that reason i would keep my receiver and i would use it as often as possible to exercise that vital link of the dedicated and informed to the audience that craves knowledge and information.
   Especially the music programming of your local non commercial station that offers it's airwaves to the collectors and music lovers who dedicate themselves,without recompense,to spreading their knowledge and sharing their collections with the public.This is a rare,and getting rarer, unfortunately.
    I think we will lose a lot when this eventually goes away,or shrinks and is overshadowed by the easy internet access to music.
    The weak links in the music programming of XM/Sirius are many,but it does provide a great variety of music and some earnest commentary on it.
   Now is the time to go give your FM receiver a big hug and listen to those local goons,the fanatics of Bluegrass,the garage Rock heads,the mouldy fig Jazz impresarios,the hipsters and the flipsters,the high and flighty  guys going for Baroque and the endless drone of industrial and independent small press Rock that survives despite the drooling D.J.'s. It's alive,it's radio,it is the voice of actual people who make mistakes and don't really care because we all make mistakes. We need it, and it may be the last hearth we may have to sit around,one on one.
    So save your radios.Use your radios.We need them now more than ever.
It easy actual a tuner not a receiver. I really like the way you explained that. Thank you.

Much like obsolete cameras for which film is no longer available, an FM tuner, in a post FM world, would be nothing more than a static display piece. 

I suspect that initially, the value could plummet but in a 100 years, it may be worth some real money. 

Feel better now? 
Within five years that Mac will become just another dust collector. Sad but true!