My 2 cents, I don't think these cars will drop in value any time soon or simply at any time. I think they will stay relatively pricey, I just don't see them as saturated as the M3 was. It's still rare to see an M2 on the road and I think that plays a big role into market demand.
Also, heres something to look at
https://youtu.be/MRaLC8-EQIQ
Skip to 5:25.