The React Native development team seems to have planned a re-architecture of it as an answer to the issues these groups have found and which lead them to turn away from it.
One big pain point for React Native seems to be the so called "dependency hell", where every project has to rely on a plethora of third party npm dependencies which constantly break even with the smallest updates. The whole tooling and setup of the framework seems very fragile and as a result developers are constantly having to spend time "fixing" stuff to get their projects working. Several posts in the React Native subreddit have expressed frustration over these issues. From what I gather Flutter does not suffers from this particular problem and it's setup/tooling is rather painless. And in term of app performance Flutter appears to do better as it doesn't relies on a javascript bridge like React Native does (which seems to be the reason for slow performance at times).
Could all these be signs that it is the beginning of the end (so to speak) for React Native as the "latest and greatest" and could Flutter end up supplanting it as the framework of choice to develop for both platforms?