I don't think Amazon is going to accept Bitcoin as payment method, they would have already done so if they were really interested.
BTC is still nowhere in retail terms. I would've thought most merchant figures would back that up. They did it for publicity, looking cool and hoovering up a few early adopter dollars.
It'll be a good while, if ever, before accepting it becomes a commercial imperative and that's when Amazon would start to take it seriously.