Nobody thinks watchOS should be like macOS, right?
So for the next years, I would expect iOS and macOS to share, what makes sense, but keep the UI separate, where it matters (touch/pen vs mouse/keyboard).
With the iPad pro and the iOS 11 features, they aren't unifying so much as creating another usage category to appeal to more people.
Everything from how big the area for a tap is, to how to work with highlights, how dragging work, how things are aligned, what deliberate limitation etc, are different between macOS and iOS.
But if you can give me a Macbook's power with a touchscreen and detachable keyboard - "Here, take my money!" :)
Also. Did you ever see anyone using that launcher as primary interaction?
I'll be surprised if they're still selling Macs in 5-7 more years.