This article might be interesting for you.
https://www.investopedia.com/articles/company-insights/090216/when-will-amazon-accept-bitcoin-amzn.asptl;dr
You could still purchase Amazon gift cards with Bitcoin and use it. So it's pretty much buying with Bitcoin. Since there are companies that were already doing this, I don't think reinventing the wheel would be a breakthrough.
Surely this would be the moment which would solidify mass adoption of the currency?
Let's put the browser extension aside, Amazon accepting Bitcoin would be good for the ecosystem. But, IMO we need more than that. We need everyone, and every major retailer to accept Bitcoin.