Flutter will stay relevant exactly as long as Google believes it is relevant. I'd say the jury is still out on it but IMHO things are looking increasingly like they don't have a winner on their hands in terms of developer adoption. I've yet to encounter a single Flutter app in the wild. I'm not aware of anything mainstream using it.

You can tell a lot by what Google is talking about and what they are not talking about or actively avoiding talking about. Right now they are not talking a lot about Flutter (and even less about Fuchsia). Given the timing, you'd expect them to be full on shipping Flutter everything with the upcoming Android. Not a thing. Not happening at all. What ever they are doing with it, eating their own dog food is not it this year.

They just unceremoniously killed Duo after it was long clear to world + dog that that was the only sensible thing to do after that clearly failed to bring in a lot of new users from more fashionable things like Skype, Facebook Messenger, iMessage, Zoom, or Google's own Meets. Duo never came close to being in the same league. Same thing with Flutter. It's not happening and probably never will. It's a dead horse, they've flogged it for a while, it's not going anywhere. The next logical move is to shelf it.

Jetpack Compose on the other hand looks like it will be the main thing to do Android with this time next year. They are shooting for a release in 2021. 2021 Android will hit Beta probably in Spring. I'd say Jetpack Compse is well on track to release along with that around the same time.

I played with Jetpack Compose a few weeks ago; it's great. It might actually interest me in doing some proper mobile development. The old android SDKs with it's mess of XML, lots of java legacy, convoluted build tooling etc. is not very compelling to me. Jetpack compose does away with pretty much all of that. Good riddance.