Looking at their free shipping policy, amazon appears to operate mainly in the united states. Their shipping network isn't equipped to function well on an international basis. If north america represents amazon's largest consumer demographic, I think they'll wait for international expansion to grow before including widespread support for crypto currencies.
The large majority of americans have access to debit/credit cards/paypal/gift cards & including support for crypto likely won't make a difference in their domestic US markets. Internationally however the percentage of consumers with access to electronic payment can decline. Crypto having a lower bar to entry for consumers could make it an attractive method of digital payment in areas like africa which are prone towards having unstable currencies and perhaps not the most cost effective methods of electronic payment.
What amazon's precise business plans are is anyone's guess. Business is going very well for them atm. Their key thing is efficiency. Eliminating "brick and mortar" stores gives them an efficiency advantage over traditional stores. Whether amazon expands and includes support for crypto may depend upon regulation. Tariffs, taxes, fees on shipping. Import/export regulations from US based businesses to foreign countries. Whether amazon can establish distribution centers in other countries who will be open to them operating there.
I don't think amazon will include support for crypto in 2018. But there is
https://purse.io/ (which I have never used btw and can't comment on) it could make direct crypto support redundant to a degree. Paying for things on amazon with crypto may not be that difficult. What might be hard is finding shipping support, especially for international residents.
It's likely that if Amazon does accept crypto, they will merely outsource that to an intermediary who processes crypto transactions and immediately converts to the local currency where they are shipping to or operating at. I don't see Amazon as being too interested in holding crypto, but only using it as a means to appeal to anyone who might not otherwise buy something from Amazon, and with the amount of sales they presently do, it's not likely to be meaningful.
As for Amazon's efficiency, they're actually acquiring brick and mortar stores now (there have been multiple acquisitions recently designed to give them a physical footprint, Whole Foods being the largest), and they're generally doing so because a purely online presence presents particular obstacles they haven't been able to solve. And Amazon already has large scale operations outside of the US, recently announcing they were expanding their operations in Mexico and breaking in to Brazil in a more meaningful way. I don't particularly think crypto will play a meaningful role in foreign markets as much as the US, if they ever decide to go that route, and even then, I don't see it ever being a meaningful needle mover for the company.
