I disagree.
How come with just simple reasoning they will start dumping anything?
No, I don't think that is the key to make them sell whatever asset they hold.
Since someone on the other end is still buying, the value won't drop just yet.
Plus, they will need to worry about "competitors". (another group of rich people) If this group have a goal of increasing the value more by holding it then risk will go higher for the sellers that you mentioned.