I am quite sure they wouldn't do that anytime soon. I think The Amazon company might consider investing in bitcoin but would never accept it as payment. Why? there would be too many complications in their transactions because of bitcoin's volatility. The prices would change on a daily basis and would simply be an added workload/process which will cost them more money. Oh yeah, imagine millions of refunds in bitcoin that they have to process considering the value might go up or down the next minute/day. I'm sure there will come a time for this idea when mass adoption happens, though.
I agree with you, investing in the crypto market if the price of bitcoin has a sharp increase is what Amazon can consider but if required they should consider bitcoin and crypto to become a payment method, that would be impossible when it has so many reasons and processes that need them to handle. The most typical is the regulations, the government still does not have a clear regulation on crypto, a large company will not be able to accept an illegal product, another problem is that value has too much volatility, which can always create injustice for buyers