I really think SwiftUI is hamstrung by trying to create a DSL that can describe a UI spanning everything from your watch to a desktop. The Apple world is starting to feel more like Google and MS with multiple UI frameworks coming out of different groups and no clear communication on what the long term plan is or expectation from developers. From what I can see though it looks like Catalyst is still very much a thing and I don't think that UIKit is going away anytime soon.