An important reason why Amazon won't be accepting Bitcoin anytime soon is because a lot of their sales come through 3rd party sellers.
So, even though Amazon is the sales platform, you're actually buying from an independent seller and Amazon is just handling the order processing (and sometimes fulfillment). This means that individual sellers would have to sign on to accept Bitcoin.
Just managing this process and dealing with all the complaints from sellers who aren't happy with the BTC/USD rate at the time of sale thinking that Amazon screwed them somehow would make this a nightmare for Amazon. Amazon only disburses money to sellers every two weeks, so you could have sellers who sold a product when BTC was at $4,500, but it's at $3,500 by the time it gets disbursed.
The technical implementation wouldn't be as easy as just adding another payment option, so I'd be willing to bet everything I have that they won't be accepting BTC anytime soon.
I agree that a large percentage of Amazon´s sales come through 3rd party sellers.
However, you are completely mistaken about how this relationship between merchant and Amazon works.
Your worries are unfounded, because Amazon not only handles the processing but also the payment.
This is why you aren´t redirected to a sketchy website where you enter your CC data and instead
use the CC data stored at Amazom from your previous purchases.
How am I mistaken? Someone has to take on the risk, so it's either Amazon or the 3rd party seller.
Amazon is willing to take on processing risk because they have security measures in place to minimize fraud and with millions of transactions per year, they can pretty accurately estimate what their loss percentage is and build it into their margins. You can't do that with exchange rate volatility.
It sounds like you're suggesting that Amazon would take on volatility so it's not an issue for merchants. If so, there's no way for Amazon to mitigate this like they can with risk of fraud. Even if Jeff Bezos personally thought Bitcoin is undervalued, it's not likely that all shareholders would agree.
The other option would be for Amazon to do conversions from BTC to fiat on the spot for each transaction. You eliminate volatility risk, but converting each transaction comes at an added cost.
What's more likely to happen first is for Visa/Mastercard to start allowing BTC at some point since that's how it works with other currencies. If someone wants to buy something on Amazon using a European credit card, the buyer pays with Euros and Amazon receives dollars. Visa/Mastercard takes on the currency risk, but they build in a favorable exchange rate to account for volatility. If you've ever bought something via credit card while traveling abroad, you can see this on your statement at the end of the month. If they were to do the same with BTC before it becomes a more stable currency, they'd have to provide a really poor exchange rate to account for the extreme volatility we see today.