I think you're right that Amazon won't miss this boat (but someone might be able to do it better than them). Amazon are already looking at printing instant-order dash buttons directly on products.

I think the things that could threaten amazon's core business one day are:

3D printing. Whether the designs are free or paid for, its not a given that you'll buy the designs through Amazon. You might get the filament through them, but that's a fraction of the value they currently capture.

Sharing, rental and communal ownership. Many of the things I buy from Amazon are never used full time. Whether at a local or national scale the norm could shift to communal resources rather than private ownership. Particularly as city apartments get smaller and have less storage.

Direct ordering from China or other producers. Amazon have already lost this to alibaba. If we started ordering more everyday things direct, this could hit Amazon.

Full AI Ascension. If we completely leave corporeal existence behind, it would put a dent in Amazon's business. Although, on second thoughts, we'd probably be running on AWS...