The values have been steady overall for the BJ-8. Is that a sign that we have seen the top of the market? As always, we start with market demand. How many buyers are there for how many cars? In my opinion, the number of cars is actually increasing due to the feverish work of the restoration community. Yes, i know they are not "new" cars, but they are not really marketable as vehicles until they are restored. My sense, and I have NO data to support this, is that more good to excellent condition Healeys are entering the world than leaving it through damage, decay or neglect. And this is true for all collectible cars of a certain value.
At the same time, I believe buyers for Healeys are exiting the pool faster than they are entering it. Through age and death, the people that want these cars either can no longer manage them or have passed them on to younger people who may lack the prior owner's enthusiasum. I think the bulk of the buying market is between 60 and 75 years old, with most of those who are older than 75 getting out of it and most of those who are younger than 60 having interest in other vehicles, or no interest in classic cars at all.
Politics are a factor here. "my generation", while eager to help the environment, grew up loving the automobile. The younger generation sees the automobile as a problem. You just don't have the pool of replacement buyers to begin with, even if you could transfer our love of these cars to younger people.
In summary, the end is not here, but as someone above pointed out, the Model As and Ts and even the Ford T-Bird sort of point the way.