Apple has signaled that SwiftUI is where they are going and will continue iterating on it for many years to come. They are like old-school Microsoft in that way. Version one is certain to be incomplete, but they will stick with it over the long haul.

Apple certainly has done a much better job of picking a development strategy and iterating on it than Microsoft has over the past couple of decades.

They will continue to use UIKit / AppKit for their own apps. They will just make it so that doing so will require a private entitlement. 3rd party apps will be restricted to SwiftUI.

Apple is very much in the camp of maybe tolerating third parties, but only so long as they only ever do stuff in the bounds of what Apple wants them to do