[kitsunesoba]

I wouldn't worry too much about AppKit going anywhere any time soon. It's probably in a similar position to where Objective-C is, where it's not receiving a whole lot of additions/iterations, but it'll stick around for years to come because of how much of the OS and how many third party apps still rely on it. It's a good idea to become familiar with SwiftUI but I think Cocoa is in a much better position than say Carbon was several years ago.