I expect that Amazon will not until there are federally regulated options and there is enough consumer demand.

There are already complaints from overseas customers about using normal foreign exchange since the banks take about 3% of the proceeds and when exchange rates change, customers may find that it costs them more to pay for the purchase than they thought when they made the purchase.

I really see nothing in this for Amazon.

I expect that an entirely new generation of digital currencies will be developed before cryptocurrencies gets accepted. The volitility and prevasive problems related to theft, use by criminal organization for money laundering and extortion is going to keep any sensible legitimate business very clear from any such interactions using this currency.