As tittle says will amazon accept bitcoins in the future?
Depend on growing of bitcoin and count of users. Because if there are not people use bitcoin Amazon not will accept. Bitcoin is new on the world, needs more time for it until accepted by Amazon.
Since Microsoft and Steam have introduce bitcoin payments, Amazon also should accept it soon.
Also, they will check if they are earning a profit from those deals else they might use it on trial basis.
I think Amazon does't take risk with accept bitcoin soon for today, because price of bitcoin its self is hight fluctuating it is not yet stable. And bitcoin also not too famous.