Considering the iPad retina (any model) is using a MacBook monitor as it’s display (effectively) there’s no reason Apple should not have already combined the two. (Hint: there’s a reason [a hardware roadmap] that the new MacBooks — the NotAirs- have 12in screens…).
There’s so little, minute connections from monitor to the computer on a laptop that making it detachable just makes sense.
It would not make sense for some users, and so shouldn’t be a feature in all MacBooks but modularity is the way of the electronic future and makes a lot of sense for power users.
I think we will likely see a touch screen in the next iMac and in at least top-end 13" and 15" MBP soon after.
A power user MBP would be a return to the 17" option with a detachable iPad for a monitor, with a similar option for at least the 15".
The Ax (A10/11/15 etc) chip could take over when the MacPad (coined it ;) ) is detached, the core (laptop) could easily connect via WiDi to multiple MacPad/iPad displays. A simple drop-in mount stand could turn the pad into a standing monitor.
Apple could upgrade the core every year and keep the pad on a 2 or 3 year cycle; optionally selling you a whole new Mac or just a Pad. If your core was up to date but your Pad behind the times, just upgrade the pad.
Apple’s next move shouldn’t be about catching up; the next move is to push the tech forward.