I'd imagine it will take much more than 1.0 to get close to parity with the OS. Even if we assume it will always be 90% of the full OS experience (which is fine for the vast majority of use cases).
And in cases where you're using platform-specific feature that Flutter doesn't support yet, then your experience will be no different -- the burden remains on you to write platform-specific code.
It's unclear to me that this is a sticking point.
It's also assuming that the Flutter team wouldn't consider do that considering they have that kind of information available to them -- it's in their best interest, after all.
I agree with the other commenter -- don’t expect any close cooperation between Flutter and Android because that’s just not how Google (and other huge companies) tends to work.