I still think that macOS and iOS will merge at some point in the future. Some folks predict an alternative theory: iOS running along Mac OS X on a Mac.
A friend made this prediction: "The next iMac will be a touch enable computer either through the screen or through a multi-touch tablet and will have macOS along with iOS built in. This would greatly increase the marketing potential for the apps and advertising."
And in a long-ago (about 2010) ZDNet column, tech writer Adrian Kingsley-Hughes said he thought we might see iOS running alongside Mac OS X (now just macOS) proper.
"Pre iPad, it made little sense for Apple to even think of putting the iPhone OS on the Mac, since the apps were specifically designed for a small screen. But with the iPad, Apple is now building quite a repository of apps designed for a far bigger screen," he wrote. "It’s not hard to imagine apps …. designed for the iPad working on a MacBook, MacBook Pro or MacBook Air. Rather than being driven by a touchscreen, the OS would simply take commands via the keyboard and trackpad. The iOS could be a dual boot OS on a Mac, but what would really integrate the iOS with Mac OS would be if iOS were also accessible via Mac OS."
Personally, I can't imagine a Mac that would dual boot into Mac OS X or iOS. They'll run concurrently if the ability to run iOS apps ever comes to a Mac (though I’m dubious it will).
However, Kingsley-Hughes said that "the addition of iOS on a Mac would be a value add to an existing platform, rather than a replacement for an iPhone or iPad."