As I said, there's one aspect of macOS Mojave that we really do have to talk about.
Macs and iOS devices have been getting closer and closer to each other in terms of functionality, and now Apple is bridging that gap with an announcement that the company will be making it easier to port iOS applications over to macOS at its WWDC.
Apple has already been testing its new frameworks, with the recently revealed News, Stocks, Voice Memos, and Home apps that Apple introduced with Mojave all actually being ported versions of the iOS apps. According to Apple, the cross-platform porting is made possible by integrating elements of iOS's UIKit frameworks directly into macOS, alongside the existing AppKit framework used on desktop.
The point during the keynote where Apple announced this was odd - they put up a slide with the question if Apple will ever merge iOS and macOS, followed by a slide that simply said "no". However, they then followed by saying that a large part of all the mac OS Mojave features they just announced were actually ports from iOS, which really takes the wind out of that seemingly definitely "no". We're not merging iOS and macOS, but by the way all the new apps you just saw are iOS apps!
In any event, this is the Marzipan project Mark Gurman scooped late last year, and it will present a massive sea change for Mac and iOS developers alike. With how popular iOS is compared to macOS, all your favourite macOS applications will eventually be iOS applications ported over to run on macOS. It simply makes very little economic sense to have two separate applications fully optimized for each of the two platforms; it's much easier to develop an iOS application that oh-by-the-way also runs on macOS.
So no, iOS and macOS aren't merging in the sense that they're going to be the same operating system, but once most macOS applications are just ported iOS applications, can you really argue that the distinction between the two platforms really matters?