Hasn't this been the plan for like a decade now? I know some of their products run Fuchsia, like the Nest displays, but no word on main Android devices

If they did ever have such a plan, they've clearly long since abandoned it. I bet they entertained the idea at one point but it was never seriously put into action.

No

As far as I can tell, Google has never stated that as a goal. It had always been a hypothesis.

The plan was initially to merge Android & Chrome and create "Andromeda" - https://arstechnica.com/gadgets/2016/09/android-chrome-andro...

Then they decided that Fuchsia was going to be the way forward - https://www.thurrott.com/mobile/android/117587/google-allege...

Now the latest is that they're once again merging Android & Chrome - https://www.androidauthority.com/chrome-os-becoming-android-...

But Fuchsia is still being actively developed, not sure to what end - https://fuchsia-review.googlesource.com/q/status:open+-is:wi...

As far as I remember, Fuchsia is used for all Googles smart devices now. So maybe just for them?