The thing that's going to blindside Amazon isn't anything happening this moment. What's going to blindside them are the unknown authors out there today... the ones they don't care about in the least... who blow up in a year or two. And they will blow up on other vendors. And they will publicly state that they have no love for Amazon because Amazon had no love for them.
This is always how the giants fall. It's not the big dogs today, because most of them are white listed. It's the big dogs of tomorrow.
I know saying this will catch me some flack, but whatever. A lot of the big dogs (not all, but a lot) in zon today were playing in the amazon pond 2014 and prior. They built their baes in a totally different ecosystem than exists today (edit: different in terms of launching a book and reaching readers). They are going to stick with zon because it's where they built their base of operations.
But there's a new generation of authors (let's define "generation" as being every three years in the self-pub industry) that zon is taking the boots to hard and heavy. These authors are going to be the big dogs down the road, and they won't forget how they were treated.
Zon is behaving like an unstoppable juggernaut and has no idea the level of damage it is doing to itself. It can't really be seen today, but in five years, it will be obvious. At which point they'll have to try and repair the damage they are doing today (and usually companies fail in that endeavor).
But, I gotta admit, if I was worth $80B i don't know if I'd give a &*%$ either.