I am especially nervous about Flutter since they don't even have to abandon it. If they don't keep pace with new OS releases, there is no great way to recoup your investment in Flutter. You are just stuck without an outdated looking app or forced to do a full rewrite in the native frameworks.
Keep in mind that Flutter is an open-source project with an active community. There's nothing particularly special about the built-in widgets that the Flutter framework provides; other developers can make and publish their own widgets easily enough if the built-in widgets are insufficient.
