Amazon likes 3rd party sellers because they basically give them free credit (3rd party seller pays for product, Amazon only pays them after the product was sold).
Also, 3rd party sellers shoulder a lot of the risk. If a product doesn't sell, or needs to be recalled, etc., Amazon doesn't care -- it's the seller's responsibility.
So I think Amazon really likes 3rd party sellers. They probably only want to get rid of them if a product gets popular enough (they want to sell it themselves) or if a product category comes with too much issues (counterfeits).
Also, 3rd party sellers shoulder a lot of the risk. If a product doesn't sell, or needs to be recalled, etc., Amazon doesn't care -- it's the seller's responsibility.
So I think Amazon really likes 3rd party sellers. They probably only want to get rid of them if a product gets popular enough (they want to sell it themselves) or if a product category comes with too much issues (counterfeits).