It is unlikely that we will see the death of the Amazon in the near future. However, I think that this is possible if cryptocurrencies become even more popular, and Amazon does not have time to implement them in its platform in time. Also, if OpenBazaar or similar platforms can offer people a better crypto product than Amazon, there is a chance that Amazon’s monopoly will be destroyed, at least in part. I would like to see something like this someday.
As the cryptocurrency grows and as OP expected that it could happen to go mainstream together with the amazon is not possible. There will be mo destruction going to take place for amazon though it will be a competition. Remember that the world is huge and has avast clients to cater with so there is nothing wrong when there will be another company competing the world's known market.