Is that an OS update? Do you really need iOS apps on the Mac? How about having decent apps in the actual native apps store?
They obviously can't put all the under-the-hood changes on the slides as there's probably a ton of stability fixes and hardening going on behind the scenes.
There are good iOS apps for a lot of things, if they can easily be adapted to run on the Mac as they demonstrated by porting the News app it can only be good for the ecosystem. The apps won't look like they are running in an iOS simulator and you use a mouse pointer to do touch actions. It'll be a normal native app that shares code with iOS.
Additionally, if I want to bring an iOS app to the Mac, then it'd be great to not have to figure out the Cocoa version of a certain UIKit view and then rewrite all of the code to fit.
I can't imagine this would translate to some next-level version of universal binaries, but who knows what it'll be like in a few years.
You still need to adapt it to native UI conventions like the menu bar, you just won’t need to rebuild the entire UI from the ground up in AppKit anymore.
Maybe Facebook will make a Mac client for Messenger (messenger.com works, but some people might prefer a desktop version). Maybe Netflix will have a Mac client (they already have one in the Windows store). We could get Google Maps as an alternative to Apple's native Maps app. Slack could throw away their Electron battery-guzzler and replace the Mac version with one based on the native iOS codebase.
Not every app wants or needs a Mac port, but there are plenty of cases where it could be useful.
I love apps that allow me to work on an iPad while I'm on the tube, then pick right up where I left off on the desktop. It’s the best of both worlds.
A good example is Bear Writer[0], a Markdown-based writing and notes app. The Mac app, while fully featured, is based on Electron. Without knowing anything about this new system I’d think these changes would allow the developers to create a native Mac app at least as easily as an Electron web app.
This is something pretty much everyone I know wants that has had both a Mac and iPhone.
There are great iPhone apps and they usually don't have a Mac version. You're stuck whipping out your phone to use some app even though you're already using your laptop.