The M2 will Never be a collectors car, mas produced will always depreciate. The 1M was a test car for the M group to define a market below the M3. It was designed to be a Limited edition car, even though it wasn't advertised that way.
The 1M will always be a limited number Collectors car. And there will always be a Collectors market for the car.
Best BMW I have ever owned and I have owned them for almost 40 years.