I don’t think convergence is their current goal. UIKit is simply a more “modern” API for writing GUI apps. AppKit hasn’t been evolving much in the past decade.
That’s just not true. AppKit has evolved a lot since 10.6. Big changes in Lion and lots of incremental improvement since.
UIKit may be more modern in some specific aspects, but it’s also far more limited. Here’s a good post highlighting some of the most obvious differences:
https://pilky.me/appreciating-appkit-part-1/
