He might be referring to Apple abandoning SwiftUI as there’s a rumor going around about it.

Ahh well that’s very different and equally unlikely to be true! Current and previous household name employers are all-in on SwiftUI and it is unquestionably a valuable thing to learn. Something new always comes along but I’d bet a lot of money we’re not going back to UIKit

Any sources for this? Reason I'm asking is I have some old knowledge in Objective-C, earlier Swift and AppKit/UIKit and I'm considering brushing up my Swift and also learn SwiftUI.

Rumors are worth exactly what you pay for them.