Brian will probably have better insight into this, but my guess that (and I've heard Brian say) that UIKit will be around for years to come. I've taken a few SwiftUI courses, and found that it can be faster in some ways, but also super frustrating with nested elements that are hard to read, with XCode being really buggy still, and also you're pretty constrained to a few layouts. It's probably okay for many apps, but I've worked with a few projects where UIKit and stackviews were just so much clearer, it seemed.