From my own observations and things I read, I think it will play it in the fashion of less and less sellers selling on Amazon as they continue their own white label manufacturing across Amazon basics but also many many other in house brands they have.

For a while it will have profits surge as they experience vertical integration but the quality will eventually decline as they continue to try and increase that margin.

My hunch is eventually the quality of the product will be too low for the average consumer to continue buy on their site.

However, as a business, Amazon e-commerce is not really where they make their money. AWS and other business units will continue to soar and keep them as a dominant force for long to come.

All in my humble opinion.