Fascinating read... https://stratechery.com/2017/amazons-operating-system/
It's a UI. If you think Windows is just a UI, then yeah, I guess it might be the next operating system. But no, it's unrelated
Alexa is dumb as fuck. It has a long long way to go before it's called AI.
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That was intentional but it doesn't change the fact that we are nowhere closer to AI.
The correct term is platform. OS is slightly different. There can be multiple platforms who are not necessarily competing, so I'm not sure what you mean by next