When/if Google ditches Android you think they will give up the echo system? You think suddenly Android apps wouldn't run on Fuchsia? It would be a seamless transition(look at how they did it on the Nest Hub).

All the "cool" new Google features and performance upgrades may be Fuchsia only. I wouldn't bank much on Amazon. They just need an OS to run their readily disposable devices. I don't see them putting too much effort into this.

Google is going the hold the hand of manufacturers and ease them into it.

At least if Google had any sense this is how it would be done.

I think that's exactly what this is; it functions as insurance of sorts for the mobile world - such that they aren't totally locked out of a feasible platform (see tablets especially for both ) and also a "why not" for MS & Amazon both. It gives MS a starting point for an Android SDK + existing Amazon Android apps - and Amazon can bolster their offerings which currently are fairly barebones.

It could amount to little, of course. Even iOS apps on MacOS as a concept and practice has not remotely the luster ardent Apple acolytes predicted, certainly not yet even 7 months in.

Fuchsia is a kernel, not operating system. Google intends to swap Linux under Android to Fuchsia. One reason is the bad track record of Linux supporting device drivers.