If yes, expand a bit. Do you think they're going to convert some cash into BTC, or will they just accumulate by accepting btc as payment?

If no, why not? Tesla, SpaceX, Twitter, Square, Paypal, Visa, etc are all adopting, does the largest ecommerce platform not have anything to gain here? I think they're more likely to have BTC than go out of their way to build their own crypto like facebook.