This is an insightful 2005 article by John Siracusa on the lessons from Copland, Apple’s attempt to turn Classic Mac OS into something modern, and predictions/advice for Mac OS X on future-proofing:
This is a follow-up article where the author re-visited his predictions:
And now we have Apple introducing a new language: Swift
Introducing a new language is interesting. We have Dylan (failed), Dart (maybe), Go (doing quite well), and Rust as “modern” mainstream languages aimed at replacing some previous language. Objective-C is only successful because the iPhone and iPad are successful.