I think this is a symptom of internal rivalries at Google. Seems like a combination of Dart (arch-rival to Go) and ChromeOS (arch-rival to Android).
That's not necessarily a bad thing -- Google's M.O. has always been to try lots of different things at once. But it may mean they literally don't have a solid long-term plan for it yet.
I was being a little tongue-in-cheek, sure, but only slightly. They're both fairly recent languages, both representing a vision of how to fix the mistakes of the past. I'm sure the leaders of the teams see each other as rivals.
Why should I rewrite my Android app just because Google can't work out their internal politics?
And yes, I know that you'll probably be able to run Android apps on Fuchsia, but what about bitrot? Will JVM-language based Android be put on Life Support?
That's not necessarily a bad thing -- Google's M.O. has always been to try lots of different things at once. But it may mean they literally don't have a solid long-term plan for it yet.